WO2024073145A1 - Methods and devices for adaptive loop filtering and cross-component adaptive loop filter - Google Patents

Abstract

Methods and apparatus are provided for improving the coding efficiency of adaptive loop filter (ALF). A decoder obtains one or more spatial neighboring samples associated with a current chroma sample. The one or more spatial neighboring samples are from at least one of following signals: (i) a chroma prediction signal, (ii) a chroma residual signal, (iii) a pre-chroma sample adaptive offset (SAO) signal, or (iv) a pre-chroma deblocking signal. The decoder obtains a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample.

Description

Attorney Ref.: 186015.20176 METHODS AND DEVICES FOR ADAPTIVE LOOP FILTERING AND CROSS- COMPONENT ADAPTIVE LOOP FILTER CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is based upon and claims priority to Provisional Application No. 63/412,345 filed on September 30, 2022, the entire content thereof is incorporated herein by reference in its entirety. TECHNICAL FIELD [0002] The application is related to video coding and compression. More specifically, this application relates to methods and apparatus on improving the adaptive loop filtering process. BACKGROUND [0001] Digital video is supported by a variety of electronic devices, such as digital televisions, laptop or desktop computers, tablet computers, digital cameras, digital recording devices, digital media players, video gaming consoles, smart phones, video teleconferencing devices, video streaming devices, etc. The electronic devices transmit and receive or otherwise communicate digital video data across a communication network, and/or store the digital video data on a storage device. Due to a limited bandwidth capacity of the communication network and limited memory resources of the storage device, video coding may be used to compress the video data according to one or more video coding standards before it is communicated or stored. For example, video coding standards include Versatile Video Coding (VVC), Joint Exploration test Model (JEM), High-Efficiency Video Coding (HEVC/H.265), Advanced Video Coding (AVC/H.264), Moving Picture Expert Group (MPEG) coding, or the like. Video coding generally utilizes prediction methods (e.g., inter-prediction, intra-prediction, or the like) that take advantage of redundancy inherent in the video data. Video coding aims to compress video data into a form that uses a lower bit rate, while avoiding or minimizing degradations to video quality. Attorney Ref.: 186015.20176 SUMMARY [0003] Embodiments of the present disclosure provide for techniques relating to adaptive loop filtering. [0004] In a first aspect, the present disclosure provides a method for video decoding comprising obtaining, by a decoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of the following signals: (i) a chroma prediction signal, (ii) a chroma residual signal, (iii) a pre-chroma sample adaptive offset (SAO) signal, or (iv) a pre-chroma deblocking signal; and obtaining, by the decoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample. [0005] In a second aspect, the present disclosure provides a method for video encoding comprising: obtaining, by an encoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of the following signals: (i) a chroma prediction signal, (ii) a chroma residual signal, (iii) a pre- chroma sample adaptive offset (SAO) signal, of (iv) a pre-chroma deblocking signal; and obtaining, by the encoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample [0006] In a third aspect, the present disclosure provides a method for video decoding comprising: obtaining, by a decoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of the following signals: (i) a luma prediction signal, (ii) a luma residual signal, (iii) a pre-luma sample adaptive offset (SAO) signal, or (iv) a pre-luma deblocking signal; and deriving, by the decoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample. [0007] In a fourth aspect, the present disclosure provides a method for video encoding comprising: obtaining, by an encoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of following signals: (i) a luma prediction signal, (ii) a luma residual signal, (iii) a pre-luma sample adaptive offset (SAO) signal, or (iv) a pre-luma deblocking signal; and deriving, by the encoder, a filtered chroma sample based on the one or more spatial neighboring samples associated with the current chroma sample. Attorney Ref.: 186015.20176 [0008] In a fifth aspect, the present disclosure provides a method for video decoding comprising: obtaining, by a decoder, coding information associated with a coding block, wherein the coding information includes a first flag indicating that the coding block is coded with a skip mode and a second flag indicating that the coding block is coded with at least one of the following modes: an intra mode, an inter P mode, or an inter B mode, to derive new classifiers for an online adaptive loop filter (ALF) process; and deriving, by the decoder, a new classifier for the online adaptive ALF process based on the coding information. [0009] In a sixth aspect, the present disclosure provides a method for video encoding comprising: obtaining, by a encoder, coding information associated with a coding block, wherein the coding information includes information whether the coding block is coded with a skip mode and information that the coding block is coded with at least one of the following: an intra mode, an inter P mode, or an inter B mode, to derive new classifiers for an online adaptive loop filter (ALF) process; and deriving, by the encoder, a new classifier for the online ALF process based on the coding information. [0010] It is to be understood that both the foregoing general description and the following detailed description are examples only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS [0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate examples consistent with the present disclosure and, together with the description, serve to explain the principles of the disclosure. [0012] FIG. 1 is a block diagram illustrating an exemplary system for encoding and decoding video blocks in accordance with some implementations of the present disclosure. [0013] FIG.2 is a block diagram illustrating an exemplary video encoder in accordance with some implementations of the present disclosure. [0014] FIG.3 is a block diagram illustrating an exemplary video decoder in accordance with some implementations of the present disclosure. [0015] FIGS.4A through 4E are block diagrams illustrating how a frame is recursively partitioned into multiple video blocks of different sizes and shapes in accordance with some implementations of the present disclosure. Attorney Ref.: 186015.20176 [0016] FIG. 5 is an illustration of ALF filter shapes in accordance with some examples of the present disclosure. [0017] FIG.6 is a depiction of subsampled sample gradients in accordance with some examples of the present disclosure. [0018] FIG. 7 is an illustration of a geometric transformation of a diamond filter shape in accordance with some examples of the present disclosure. [0019] FIG.8 is an illustration of an online filter shape used in an ECM in accordance with some examples of the present disclosure. [0020] FIG. 9 is an illustration of a CCALF architecture, according to some examples of the present disclosure. [0021] FIG.10 is an illustration of a relative location of filtered chroma sample and its support in the luma plane for 4:2:0 chroma format with chroma location type 0. [0022] FIG.11 is an illustration of a 25-tap long filter according to some examples of the present disclosure. [0023] FIG.12 is an illustration of a filter shape for a prediction signal or before a SAO signal in accordance with examples of the present disclosure. [0024] FIG. 13A is an illustration of an adjusted ALF filter shape in accordance with some examples of the present disclosure. [0025] FIG. 13B is an illustration of various online ALF filter inputs in accordance with some examples of the present disclosure. [0026] FIG. 13C is an illustration of 1x1 and 3x3 filter shapes that are applied to the prediction samples of the ALF in accordance with some examples of the present disclosure. [0027] FIG. 14 is a flowchart illustrating a method for video decoding in accordance with some examples of the present disclosure. [0028] FIG. 15 is a flowchart illustrating a method for video encoding in accordance with some examples of the present disclosure. [0029] FIG. 16 is a flowchart illustrating a method for video decoding in accordance with some examples of the present disclosure. [0030] FIG. 17 is a flowchart illustrating a method for video encoding in accordance with some examples of the present disclosure. Attorney Ref.: 186015.20176 [0031] FIG. 18 is a flowchart illustrating a method for video decoding in accordance with some examples of the present disclosure. [0032] FIG. 19 is a flowchart illustrating a method for video encoding in accordance with some examples of the present disclosure. [0033] FIG. 20 is a diagram illustrating a computing environment coupled with a user interface, according to some implementations of the present disclosure. DETAILED DESCRIPTION [0034] Reference will now be made in detail to specific implementations, embodiments of which are illustrated in the accompanying drawings. In the following detailed description, numerous non- limiting specific details are set forth in order to assist in understanding the subject matter presented herein. But it will be apparent to one of ordinary skill in the art that various alternatives may be used. For example, it will be apparent to one of ordinary skill in the art that the subject matter presented herein can be implemented on many types of electronic devices with digital video capabilities. [0035] It should be illustrated that the terms “first,” “second,” and the like used in the description, claims of the present disclosure, and the accompanying drawings are used to distinguish objects, and not used to describe any specific order or sequence. It should be understood that the data used in this way may be interchanged under an appropriate condition, such that the embodiments of the present disclosure described herein may be implemented in orders besides those shown in the accompanying drawings or described in the present disclosure. Filter Shapes, Linear Filtering and Adaptive Clipping [0036] In VVC, ALF is applied to the output samples of SAO. Two filter shapes, 7×7 diamond shape and 5×5 diamond shape are supported for luma and chroma components, respectively, as shown in Fig 5. In Fig 5, each square corresponds to a luma or a chroma sample and the center square corresponds to a current to-be-filtered sample. The filter coefficients use point-symmetry and each integer filter coefficient is represented with 7-bit fractional precision. In addition, the sum of coefficients of one filter is equal to 128, which is the fixed-point representation of 1.0 with 7-bit fractional precision: Attorney Ref.: 186015.20176 ^^{^^} 2 ^^_^ + ^_^^^ = 128 [0037] where the number of to 13 and 7 for 7×7 and 5×5 filter shape,

respectively. A filtered sample value ^^{^}(^,^) at coordinates (x, y) is derived by applying coefficient ^_^ to the reconstructed sample values R(x, y) as follows: ^^{^^} ^^{^}(^,^) = ^^ ^_^^^(^ + ^_^ ,^ + ^_^) + ^(^ − ^_^ ,^ − ^_^)^ + ^_^^^^(^, ^) + 64^ ≫ 7

, (2) can be written as: ^^{^(} _^,^ ⁾ _{= ^} ⁽ _^,^ ⁾ ₊ ^^{^^} ^_^ ^^^ + ^_^ + − ^ ^ + ^^ − ^_^ − − ^ ^^ + 64^ ≫ 7}

and the current to-be-filtered sample is added to equation (3) as follows: ^^{^^} ^^{^} ^ 7} where

^^{^ = min^^^,^^^^−^^ ,^(^ + ^^ ,^ + ^^) − ^(^,^)^^ +} [0040] ^_^ is the

clipping index ^_^. ^_^ is derived as follows: ^_^ ^{= ^} _^ ^{2^^} ^ ^{,^ℎ^^ ^^ = 0} 2 _{^^^^^^ ,^^ℎ^^^^^^} [0041] where BD is the sample bit depth and ^_^ can be 0, 1, 2 or 3. Luma Sub-Block Level Filter Adaptation Attorney Ref.: 186015.20176 [0042] In VVC, sub-block level filter adaption is only applied to luma component. Each 4×4 luma block is classified based on its directionality and 2D Laplacian activity. First, the values of sample gradients for horizontal, vertical and two diagonal directions are calculated: ^_^,^ = ^|2^⁽^, ^⁾ − ^⁽^ − 1, ^⁾ − ^⁽^ + 1, ^^)|, ^_^,^ = |2^(^, ^) − ^(^, ^ − 1) − ^(^, ^ + 1)|, ^ + 1^)|,

^1_^,^ = |2^(^, ^) − ^(^ − 1, ^ + 1) − ^(^ + 1, ^ − 1)|. [0043] Based on the sample gradients, sub-block horizontal gradient, ^_^, vertical gradient, ^_^, and two diagonal gradients, ^_^^ and ^_^^, are calculated as ^^^ ^{^^^} ^_^ = ^ ^ , , , [0044] Indices ^ and ^ refer to the

left sample in the 4×4 luma block. As it can be seen from equation (8), the sum of sample gradients within a 10×10 luma window that covers the target 4×4 block is used for classifying that block. To reduce the complexity, only gradient of every second sample in a 10×10 window is calculated as illustrated in Fig.6. (See Fig. 6 depicting subsampled sample gradients for a 4x4 sub-block ALF classification. Gradient values of samples marked with x are calculated. Gradient values of other samples are set to 0). The values of other sample gradients are set to 0. [0045] Second, to assign the directionality D, the ratio of the maximum and the minimum of the sub-block horizontal and vertical gradients: ^_^ ^{^} ,_^ ^{^^} = max(^_^,^_^) ,^_^ ^{^} ,_^ ^{^^} = min(^_^,^_^),

[0046] and the ratio of diagonal gradients: Attorney Ref.: 186015.20176 ^_^ ^{^} ^^{^} ,_^ ^{^} ^ = max(^_^^,^_^^) ,^_^ ^{^} ^^{^} ,^{^} ^_^ = min(^_^^,^_^^), [0047] are compared of thresholds ^_^ and ^_^: Step 1: If both ^^{^^^} ≤ ^_^ ∙

_^,^ ^_^ ^{^} ,_^ ^{^^} and ^_^ ^{^} ^^{^} ,_^ ^{^} ^ ≤ ^_^ ∙ ^_^ ^{^} ^^{^} ,^{^} ^_^ , D is set to 0. Step 2: If ^_^ ^{^} ,_^ ^{^^}/^_^ ^{^} ,_^ ^{^^} > ^_^ ^{^} ^^{^} ,_^ ^{^} ^ /^_^ ^{^} ^^{^} ,^{^} ^_^ the

D is set

to 3. [0048] Each subsequent step in the D is only executed if there is no value

^{assigned to D in the previous steps. Third, an activity value A is calculated as} A _{= ^∑^^^ ^^^ ^^^^^ ∑^^^^^ ^^^,^ + ^^,^^ ^>>(^^ − 2)}

^{[0049] A is further mapped to the range of 0 to 4: ^^ = ^^^^ (^,^^) ,where {^^} =} _{{0,1,2,2,2,2,2,3,3,3,3,3,3,3,3,4}. Finally, each 4×4 luma block is categorized into one of the 25} ^classes: C _{= 5D + ^^} [0050] Each class can have its own filter assigned. Before filtering each 4×4 luma block, a geometric transformation, such as 90-degree rotation, diagonal or vertical flip, is applied to the filter coefficients, as illustrated in Fig.7 (illustrating a geometric transformation of a 7x7 diamond filter shape. From left to right: diagonal flip, vertical flip, and 90-degree rotation), depending on the sub-block gradient value as specified in Table 1. S b-bl k r di nt l Tr n f rm ti n

Table 1 Geometric transformation based on sub-block gradient values Coding Tree Block Level Filter Adaptation Attorney Ref.: 186015.20176 [0051] In addition to the luma 4×4 block-level filter adaptation, ALF supports CTB-level filter adaptation. A luma CTB can use a filter set calculated for the current slice or one of the filter sets calculated for the already coded slices. It can also use one of the 16 offline trained filter sets. Within each luma CTB, which filter from the chosen filter set should be applied to each 4 × 4 block, is determined by the class C calculated in equation (12) for this block. Chroma uses only CTB-level filter adaptation. Up to 8 filters can be used for chroma components in a slice. Each CTB can select one of these filters. Syntax Design [0052] Filter coefficients and clipping indices are carried in ALF APSs. An ALF APS can include up to 8 chroma filters and one luma filter set with up to 25 filters. An index ^_^ is also included for each of the 25 luma classes. Classes having the same index ^_^ share the same filter. By merging different classes, the number of bits required to represent the filter coefficients is reduced. The absolute value of a filter coefficient is represented using a 0th order Exp-Golomb code followed by a sign bit for a non-zero coefficient. When clipping is enabled, a clipping index is also signaled for each filter coefficient using a two-bit fixed-length code. The storage needed for ALF coefficients and clipping indices within an APS is at most 3480 bits. Up to 8 ALF APSs can be used by the decoder at the same time. [0053] Filter control syntax elements include two types of information. First, ALF on/off flags are signaled at sequence, picture, slice and CTB levels. Chroma ALF can be enabled at picture and slice level only if luma ALF is enabled at the corresponding level. Second, filter usage information is signaled at picture, slice and CTB level, if ALF is enabled at that level. Referenced ALF APSs IDs are coded at a slice level or at a picture level if all the slices within the picture use the same APSs. Luma component can reference up to 7 ALF APSs and chroma components can reference 1 ALF APS. For a luma CTB, an index is signaled indicating which ALF APS or offline trained luma filter set is used. For a chroma CTB, the index indicates which filter in the referenced APS is used. Line Buffer Reduction Attorney Ref.: 186015.20176 [0054] To reduce the storage requirement for ALF, VVC employs line buffer boundary processing. In VVC, line buffer boundaries are placed 4 luma samples and 2 chroma samples above horizontal CTU boundaries. When applying ALF to a sample on one side of a line buffer boundary, samples on the other side of the line buffer boundary cannot be used. ALF in ECM ALF simplification removal [0055] ALF gradient subsampling and ALF virtual boundary processing are removed. Block size for classification is reduced from 4x4 to 2x2. Filter size for both luma and chroma, for which ALF coefficients are signalled, is increased to 9x9. ALF with fixed filters [0056] To filter a luma sample, three different classifiers (^_^, ^_^ and ^_^) and three different sets of filters (^_^, ^_^ and ^_^) are used. Sets ^_^ and ^_^ contain fixed filters, with coefficients trained for classifiers ^_^ and ^_^. Coefficients of filters in ^_^ are signalled. Which filter from a set ^_^ is used for a given sample is decided by a class ^_^ assigned to this sample using classifier ^_^. Filtering [0057] At first, two 13x13 diamond shape fixed filters ^_^ and ^_^ are applied to derive two intermediate samples ^_^(^,^) and ^_^(^,^) . After that, ^_^ is applied to ^_^(^, ^) , ^_^(^, ^) , neighboring samples, and samples before deblocking filter (DBF) to derive a filtered sample as: ^^{^ ^^ ^^} ^^{^} ^ ^ ^ ^^ ^ ^^ ^ [0058]

sample ^⁽^, ^⁾, ^_^ is the clipped difference between ^_^^^^(^,^) and current sample ^⁽^,^⁾, ℎ_^,^ is the clipped difference between a neighboring sample before DBF and current sample ^⁽^,^⁾. The filter coefficients ^_^, i=0,…24, are signaled. The filter shape of ^_^ is presented in Fig.8. Classification [0059] Based on directionality ^_^ and activity ^^{^} _^, a class ^_^ is assigned to each 2x2 block:

Attorney Ref.: 186015.20176 ^_^ = ^^{^} _^ ∗ ^_^,^ + ^_^ [0060] where ^_^,^ represents the total number of directionalities ^_^. As in VVC, values of the horizontal, vertical, and two diagonal gradients are calculated for each sample using 1-D Laplacian. The sum of the sample gradients within a 4×4 window that covers the target 2×2 block is used for classifier ^_^ and the sum of sample gradients within a 12×12 window is used for classifiers ^_^ and ^_^. The sums of horizontal, vertical and two diagonal gradients are denoted, respectively, as ^_^ ^{^} , ^_^ ^{^} , ^_^ ^{^} ^ and ^_^ ^{^} ^ . The directionality ^_^ is determined by comparing: ^^{^^ (^^ ,^^ ) ^^^ ( ^ ^} ^^{^} = ^{^ ^} , ^^{^} = ^{^^^ ,^^^ )} ^_{,^ ^^^ (^^ , ^ ^^,^^ ^ ^ ^ ^^ ) ^^^ (^^^ ,^^^ )} [0061] with a set of

in VVC using thresholds 2 and 4.5. For ^_^ and ^_^ , horizontal/vertical edge strength ^_^ ^{^} ^ and diagonal edge strength ^_^ ^{^} are ^{calculated first. Thresholds Th=[1.25, 1.5, 2, 3, 4.5, 8] are used. Edge strength ^^ ^ ^^ is 0 if ^^,^ ≤} _{Th[0]; otherwise, ^^ is the maximum integer such that ^^ >Th[^^ -1]. E ^ ^^ ^,^ ^^ dge strength ^^ is 0 if} ^_^ ^{^} ^_,^^ ≤Th[0]; otherwise, ^_^ ^{^} is the maximum integer such that ^_^ ^{^} ^_,^^ >Th[^_^ ^{^} -1]. When ^_^ ^{^} ,_^ >^_^ ^{^} ^_,^^ , i.e., horizontal/vertical edges are dominant, the ^_^ is derived by using Table 2 (a); otherwise, diagonal edges are dominant, the ^ is derived

using Table

Table 2. Mapping of ^_^ ^{^} and ^_^ ^{^} ^ to ^_^

Attorney Ref.: 186015.20176 [0062] To obtain ^^{^} _^, the sum of vertical and horizontal gradients ^_^ is mapped to the range of 0 to n, where n is to 4 for ^^{^} _^ and 15 for ^^{^} _^ and ^^{^} _^. In an ALF_APS, up to 4 luma filter sets are

signaled, each set may have up to 25 filters. Alternative 2x2 ALF classifier [0063] Classification in ALF is extended with an additional alternative classifier. For a signaled luma filter set, a flag is signaled to indicate whether the alternative classifier is applied. Geometrical transformation is not applied to the alternative band classifier. When the band-based classifier is applied, the sum of sample values of a 2x2 luma block is calculated at first. Then the class index is calculated as: class_index = (sum * 25) >> (sample bit depth + 2). CCALF in VV Filter Shapes and Precision [0064] CCALF uses the luma sample values to refine the chroma sample values within the ALF process. As shown in Fig.9, a linear filtering operation takes the luma sample values as input and generates the correction values for the chroma sample values. The correction is generated independently for each chroma component ^, ^ ∈ {Cb, Cr} and can be represented by: ∆^_^(^,^) = ∑_(^^,^^)∈^^ ^_^(^_^ + ^_^,^_^ + ^_^)^_^(^_^,^_^) , [0065] where (^,^) is the sample location of the chroma component ^, (^_^ ,^_^) is the luma sample location derived from (^,^), (^_^, ^_^) are the filter support offset around (^_^ ,^_^), ^_^ is the filter support region in luma for the chroma component ^. The luma location (^_^

is determined based on the spatial scaling factor between the luma and chroma planes. The sample values in the luma support region are also inputs to the ALF luma stage and correspond to the output of the SAO stage. [0066] As shown in Fig.10, the CCALF filter has a diamond shape. As seen in Fig.10, for a 4:2:0 video sequence, with chroma location type 0, i.e., when the chroma samples are horizontally co- sited with the even numbered columns of the luma samples and vertically interstitial between the rows of the luma samples, the center of the diamond is aligned with a chroma sample location. [0067] CCALF coefficients have a greater degree of flexibility compared to regular ALF coefficients, since no symmetry constraints are enforced. However, two limitations are enforced: (1) To preserve DC neutrality, the sum of CCALF coefficient values is required to be zero. As a Attorney Ref.: 186015.20176 result, only seven of the eight CCALF coefficients need to be signalled in the bitstream, and the coefficient at location (^_^ ,^_^) is derived at the decoder; (2) The absolute values of CCALF coefficients are restricted to be either zero or an integer power of two, specifically {0, 1, 2, 4, 8, 16, 32, 64}. This enables implementations to use variable bit-shift operations in place of multiplications for CCALF, if desired. Syntax Design [0068] The maximum number of filters per chroma component of a picture was four in the final design of VVC. A different set of CCALF coefficients can be selected for each CTU of a chroma component. As is the case for the regular ALF coefficients, CCALF coefficients are signalled within an ALF APS. Each ALF APS contains up to four CCALF filters for each chroma component. While CCALF can be enabled at a sequence level, it can only be enabled if ALF is also enabled for the sequence. Similarly, CCALF can be enabled at picture and slice level only if luma ALF is enabled at the corresponding level. CCALF in ECM [0069] The CCALF process uses a linear filter to filter luma sample values and generate a residual correction for the chroma samples. A 25-tap large filter is used in CCALF process, which is illustrated in Fig.10. For a given slice, the encoder can collect the statistics of the slice, analyze them and can signal up to 16 filters through APS. [0070] Reference will now be made in detail to specific implementations, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous non- limiting specific details are set forth in order to assist in understanding the subject matter presented herein. But it will be apparent to one of ordinary skill in the art that various alternatives may be used without departing from the scope of claims and the subject matter may be practiced without these specific details. For example, it will be apparent to one of ordinary skill in the art that the subject matter presented herein can be implemented on many types of electronic devices with digital video capabilities. [0071] It should be illustrated that the terms “first,” “second,” and the like used in the description, claims of the present disclosure, and the accompanying drawings are used to distinguish objects, and not used to describe any specific order or sequence. It should be understood that the data used Attorney Ref.: 186015.20176 in this way may be interchanged under an appropriate condition, such that the embodiments of the present disclosure described herein may be implemented in orders besides those shown in the accompanying drawings or described in the present disclosure. [0072] FIG.1 is a block diagram illustrating an exemplary system 10 for encoding and decoding video blocks in parallel in accordance with some implementations of the present disclosure. As shown in FIG.1, the system 10 includes a source device 12 that generates and encodes video data to be decoded at a later time by a destination device 14. The source device 12 and the destination device 14 may comprise any of a wide variety of electronic devices, including desktop or laptop computers, tablet computers, smart phones, set-top boxes, digital televisions, cameras, display devices, digital media players, video gaming consoles, video streaming device, or the like. In some implementations, the source device 12 and the destination device 14 are equipped with wireless communication capabilities. [0073] In some implementations, the destination device 14 may receive the encoded video data to be decoded via a link 16. The link 16 may comprise any type of communication medium or device capable of moving the encoded video data from the source device 12 to the destination device 14. In one example, the link 16 may comprise a communication medium to enable the source device 12 to transmit the encoded video data directly to the destination device 14 in real time. The encoded video data may be modulated according to a communication standard, such as a wireless communication protocol, and transmitted to the destination device 14. The communication medium may comprise any wireless or wired communication medium, such as a Radio Frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network, such as a local area network, a wide-area network, or a global network such as the Internet. The communication medium may include routers, switches, base stations, or any other equipment that may be useful to facilitate communication from the source device 12 to the destination device 14. [0074] In some other implementations, the encoded video data may be transmitted from an output interface 22 to a storage device 32. Subsequently, the encoded video data in the storage device 32 may be accessed by the destination device 14 via an input interface 28. The storage device 32 may include any of a variety of distributed or locally accessed data storage media such as a hard drive, Blu-ray discs, Digital Versatile Disks (DVDs), Compact Disc Read-Only Memories (CD-ROMs), flash memory, volatile or non-volatile memory, or any other suitable digital storage media for Attorney Ref.: 186015.20176 storing the encoded video data. In a further example, the storage device 32 may correspond to a file server or another intermediate storage device that may hold the encoded video data generated by the source device 12. The destination device 14 may access the stored video data from the storage device 32 via streaming or downloading. The file server may be any type of computer capable of storing the encoded video data and transmitting the encoded video data to the destination device 14. Exemplary file servers include a web server (e.g., for a website), a File Transfer Protocol (FTP) server, Network Attached Storage (NAS) devices, or a local disk drive. The destination device 14 may access the encoded video data through any standard data connection, including a wireless channel (e.g., a Wireless Fidelity (Wi-Fi) connection), a wired connection (e.g., Digital Subscriber Line (DSL), cable modem, etc.), or a combination of both that is suitable for accessing encoded video data stored on a file server. The transmission of the encoded video data from the storage device 32 may be a streaming transmission, a download transmission, or a combination of both. [0075] As shown in FIG.1, the source device 12 includes a video source 18, a video encoder 20 and the output interface 22. The video source 18 may include a source such as a video capturing device, e.g., a video camera, a video archive containing previously captured video, a video feeding interface to receive video from a video content provider, and/or a computer graphics system for generating computer graphics data as the source video, or a combination of such sources. As one example, if the video source 18 is a video camera of a security surveillance system, the source device 12 and the destination device 14 may form camera phones or video phones. However, the implementations described in the present application may be applicable to video coding in general, and may be applied to wireless and/or wired applications. [0076] The captured, pre-captured, or computer-generated video may be encoded by the video encoder 20. The encoded video data may be transmitted directly to the destination device 14 via the output interface 22 of the source device 12. The encoded video data may also (or alternatively) be stored onto the storage device 32 for later access by the destination device 14 or other devices, for decoding and/or playback. The output interface 22 may further include a modem and/or a transmitter. [0077] The destination device 14 includes the input interface 28, a video decoder 30, and a display device 34. The input interface 28 may include a receiver and/or a modem and receive the encoded video data over the link 16. The encoded video data communicated over the link 16, or provided Attorney Ref.: 186015.20176 on the storage device 32, may include a variety of syntax elements generated by the video encoder 20 for use by the video decoder 30 in decoding the video data. Such syntax elements may be included within the encoded video data transmitted on a communication medium, stored on a storage medium, or stored on a file server. [0078] In some implementations, the destination device 14 may include the display device 34, which can be an integrated display device and an external display device that is configured to communicate with the destination device 14. The display device 34 displays the decoded video data to a user, and may comprise any of a variety of display devices such as a Liquid Crystal Display (LCD), a plasma display, an Organic Light Emitting Diode (OLED) display, or another type of display device. [0079] The video encoder 20 and the video decoder 30 may operate according to proprietary or industry standards, such as VVC, HEVC, MPEG-4, Part 10, AVC, or extensions of such standards. It should be understood that the present application is not limited to a specific video encoding/decoding standard and may be applicable to other video encoding/decoding standards. It is generally contemplated that the video encoder 20 of the source device 12 may be configured to encode video data according to any of these current or future standards. Similarly, it is also generally contemplated that the video decoder 30 of the destination device 14 may be configured to decode video data according to any of these current or future standards. [0080] The video encoder 20 and the video decoder 30 each may be implemented as any of a variety of suitable encoder and/or decoder circuitry, such as one or more microprocessors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), discrete logic, software, hardware, firmware or any combinations thereof. When implemented partially in software, an electronic device may store instructions for the software in a suitable, non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the video encoding/decoding operations disclosed in the present disclosure. Each of the video encoder 20 and the video decoder 30 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder/decoder (CODEC) in a respective device. [0081] In some implementations, at least a part of components of the source device 12 (for example, the video source 18, the video encoder 20 or components included in the video encoder 20 as described below with reference to Fig.2, and the output interface 22) and/or at least a part Attorney Ref.: 186015.20176 of components of the destination device 14 (for example, the input interface 28, the video decoder 30 or components included in the video decoder 30 as described below with reference to Fig. 3, and the display device 34) may operate in a cloud computing service network which may provide software, platforms, and/or infrastructure, such as Software as a Service (SaaS), Platform as a Service (PaaS), or Infrastructure as a Service (IaaS). In some implementations, one or more components in the source device 12 and/or the destination device 14 which are not included in the cloud computing service network may be provided in one or more client devices, and the one or more client devices may communicate with server computers in the cloud computing service network through a wireless communication network (for example, a cellular communication network, a short-range wireless communication network, or a global navigation satellite system (GNSS) communication network) or a wired communication network (e.g., a local area network (LAN) communication network or a power line communication (PLC) network). In an embodiment, at least a part of operations described herein may be implemented as cloud-based services provided by one or more server computers which are implemented by the at least a part of the components of the source device 12 and/or the at least a part of the components of the destination device 14 in the cloud computing service network; and one or more other operations described herein may be implemented by the one or more client devices. In some implementations, the cloud computing service network may be a private cloud, a public cloud, or a hybrid cloud. The terms such as “cloud,” “cloud computing,” “cloud-based” etc. herein may be used interchangeably as appropriate without departing from the scope of the present disclosure. It should be understood that the present disclosure is not limited to being implemented in the cloud computing service network described above. Instead, the present disclosure may also be implemented in any other type of computing environments currently known or developed in the future. [0082] Fig. 2 is a block diagram illustrating an exemplary video encoder 20 in accordance with some implementations described in the present application. The video encoder 20 may perform intra and inter predictive coding of video blocks within video frames. Intra predictive coding relies on spatial prediction to reduce or remove spatial redundancy in video data within a given video frame or picture. Inter predictive coding relies on temporal prediction to reduce or remove temporal redundancy in video data within adjacent video frames or pictures of a video sequence. Attorney Ref.: 186015.20176 It should be noted that the term “frame” may be used as synonyms for the term “image” or “picture” in the field of video coding. [0083] As shown in Fig.2, the video encoder 20 includes a video data memory 40, a prediction processing unit 41, a Decoded Picture Buffer (DPB) 64, a summer 50, a transform processing unit 52, a quantization unit 54, and an entropy encoding unit 56. The prediction processing unit 41 further includes a motion estimation unit 42, a motion compensation unit 44, a partition unit 45, an intra prediction processing unit 46, and an intra Block Copy (BC) unit 48. In some implementations, the video encoder 20 also includes an inverse quantization unit 58, an inverse transform processing unit 60, and a summer 62 for video block reconstruction. An in-loop filter 63, such as a deblocking filter, may be positioned between the summer 62 and the DPB 64 to filter block boundaries to remove blockiness artifacts from reconstructed video. Another in-loop filter, such as Sample Adaptive Offset (SAO) filter and/or Adaptive in-Loop Filter (ALF), may also be used in addition to the deblocking filter to filter an output of the summer 62. In some examples, the in-loop filters may be omitted, and the decoded video block may be directly provided by the summer 62 to the DPB 64. The video encoder 20 may take the form of a fixed or programmable hardware unit or may be divided among one or more of the illustrated fixed or programmable hardware units. [0084] The video data memory 40 may store video data to be encoded by the components of the video encoder 20. The video data in the video data memory 40 may be obtained, for example, from the video source 18 as shown in FIG.1. The DPB 64 is a buffer that stores reference video data (for example, reference frames or pictures) for use in encoding video data by the video encoder 20 (e.g., in intra or inter predictive coding modes). The video data memory 40 and the DPB 64 may be formed by any of a variety of memory devices. In various examples, the video data memory 40 may be on-chip with other components of the video encoder 20, or off-chip relative to those components. [0085] As shown in Fig.2, after receiving the video data, the partition unit 45 within the prediction processing unit 41 partitions the video data into video blocks. This partitioning may also include partitioning a video frame into slices, tiles (for example, sets of video blocks), or other larger Coding Units (CUs) according to predefined splitting structures such as a Quad-Tree (QT) structure associated with the video data. The video frame is or may be regarded as a two- dimensional array or matrix of samples with sample values. A sample in the array may also be Attorney Ref.: 186015.20176 referred to as a pixel or a pel. A number of samples in horizontal and vertical directions (or axes) of the array or picture define a size and/or a resolution of the video frame. The video frame may be divided into multiple video blocks by, for example, using QT partitioning. The video block again is or may be regarded as a two-dimensional array or matrix of samples with sample values, although of smaller dimension than the video frame. A number of samples in horizontal and vertical directions (or axes) of the video block define a size of the video block. The video block may further be partitioned into one or more block partitions or sub-blocks (which may form again blocks) by, for example, iteratively using QT partitioning, Binary-Tree (BT) partitioning or Triple- Tree (TT) partitioning or any combination thereof. It should be noted that the term “block” or “video block” as used herein may be a portion, in particular a rectangular (square or non- square) portion, of a frame or a picture. With reference, for example, to HEVC and VVC, the block or video block may be or correspond to a Coding Tree Unit (CTU), a CU, a Prediction Unit (PU) or a Transform Unit (TU) and/or may be or correspond to a corresponding block, e.g. a Coding Tree Block (CTB), a Coding Block (CB), a Prediction Block (PB) or a Transform Block (TB) and/or to a sub-block. [0086] The prediction processing unit 41 may select one of a plurality of possible predictive coding modes, such as one of a plurality of intra predictive coding modes or one of a plurality of inter predictive coding modes, for the current video block based on error results (e.g., coding rate and the level of distortion). The prediction processing unit 41 may provide the resulting intra or inter prediction coded block to the summer 50 to generate a residual block and to the summer 62 to reconstruct the encoded block for use as part of a reference frame subsequently. The prediction processing unit 41 also provides syntax elements, such as motion vectors, intra-mode indicators, partition information, and other such syntax information, to the entropy encoding unit 56. [0087] In order to select an appropriate intra predictive coding mode for the current video block, the intra prediction processing unit 46 within the prediction processing unit 41 may perform intra predictive coding of the current video block relative to one or more neighbor blocks in the same frame as the current block to be coded to provide spatial prediction. The motion estimation unit 42 and the motion compensation unit 44 within the prediction processing unit 41 perform inter predictive coding of the current video block relative to one or more predictive blocks in one or more reference frames to provide temporal prediction. The video encoder 20 may perform multiple coding passes, e.g., to select an appropriate coding mode for each block of video data. Attorney Ref.: 186015.20176 [0088] In some implementations, the motion estimation unit 42 determines the inter prediction mode for a current video frame by generating a motion vector, which indicates the displacement of a video block within the current video frame relative to a predictive block within a reference video frame, according to a predetermined pattern within a sequence of video frames. Motion estimation, performed by the motion estimation unit 42, is the process of generating motion vectors, which estimate motion for video blocks. A motion vector, for example, may indicate the displacement of a video block within a current video frame or picture relative to a predictive block within a reference frame relative to the current block being coded within the current frame. The predetermined pattern may designate video frames in the sequence as P frames or B frames. The intra BC unit 48 may determine vectors, e.g., block vectors, for intra BC coding in a manner similar to the determination of motion vectors by the motion estimation unit 42 for inter prediction, or may utilize the motion estimation unit 42 to determine the block vector. [0089] A predictive block for the video block may be or may correspond to a block or a reference block of a reference frame that is deemed as closely matching the video block to be coded in terms of pixel difference, which may be determined by Sum of Absolute Difference (SAD), Sum of Square Difference (SSD), or other difference metrics. In some implementations, the video encoder 20 may calculate values for sub-integer pixel positions of reference frames stored in the DPB 64. For example, the video encoder 20 may interpolate values of one-quarter pixel positions, one- eighth pixel positions, or other fractional pixel positions of the reference frame. Therefore, the motion estimation unit 42 may perform a motion search relative to the full pixel positions and fractional pixel positions and output a motion vector with fractional pixel precision. [0090] The motion estimation unit 42 calculates a motion vector for a video block in an inter prediction coded frame by comparing the position of the video block to the position of a predictive block of a reference frame selected from a first reference frame list (List 0) or a second reference frame list (List 1), each of which identifies one or more reference frames stored in the DPB 64. The motion estimation unit 42 sends the calculated motion vector to the motion compensation unit 44 and then to the entropy encoding unit 56. [0091] Motion compensation, performed by the motion compensation unit 44, may involve fetching or generating the predictive block based on the motion vector determined by the motion estimation unit 42. Upon receiving the motion vector for the current video block, the motion compensation unit 44 may locate a predictive block to which the motion vector points in one of Attorney Ref.: 186015.20176 the reference frame lists, retrieve the predictive block from the DPB 64, and forward the predictive block to the summer 50. The summer 50 then forms a residual video block of pixel difference values by subtracting pixel values of the predictive block provided by the motion compensation unit 44 from the pixel values of the current video block being coded. [0092] The pixel difference values forming the residual video block may include luma or chroma difference components or both. The motion compensation unit 44 may also generate syntax elements associated with the video blocks of a video frame for use by the video decoder 30 in decoding the video blocks of the video frame. The syntax elements may include, for example, syntax elements defining the motion vector used to identify the predictive block, any flags indicating the prediction mode, or any other syntax information described herein. Note that the motion estimation unit 42 and the motion compensation unit 44 may be highly integrated, but are illustrated separately for conceptual purposes. [0093] In some implementations, the intra BC unit 48 may generate vectors and fetch predictive blocks in a manner similar to that described above in connection with the motion estimation unit 42 and the motion compensation unit 44, but with the predictive blocks being in the same frame as the current block being coded and with the vectors being referred to as block vectors as opposed to motion vectors. In particular, the intra BC unit 48 may determine an intra-prediction mode to use to encode a current block. In some examples, the intra BC unit 48 may encode a current block using various intra-prediction modes, e.g., during separate encoding passes, and test their performance through rate-distortion analysis. Next, the intra BC unit 48 may select, among the various tested intra-prediction modes, an appropriate intra-prediction mode to use and generate an intra-mode indicator accordingly. For example, the intra BC unit 48 may calculate rate-distortion values using a rate-distortion analysis for the various tested intra-prediction modes, and select the intra-prediction mode having the best rate-distortion characteristics among the tested modes as the appropriate intra-prediction mode to use. [0094] Rate-distortion analysis generally determines an amount of distortion (or error) between an encoded block and an original, unencoded block that was encoded to produce the encoded block, as well as a bitrate (i.e., a number of bits) used to produce the encoded block. Intra BC unit 48 may calculate ratios from the distortions and rates for the various encoded blocks to determine which intra-prediction mode exhibits the best rate-distortion value for the block. In other examples, the intra BC unit 48 may use the motion estimation unit 42 and the motion compensation unit 44, in Attorney Ref.: 186015.20176 whole or in part, to perform such functions for Intra BC prediction according to the implementations described herein. In either case, for Intra block copy, a predictive block may be a block that is deemed as closely matching the block to be coded, in terms of pixel difference, which may be determined by SAD, SSD, or other difference metrics, and identification of the predictive block may include calculation of values for sub-integer pixel positions. [0095] Whether the predictive block is from the same frame according to intra prediction, or a different frame according to inter prediction, the video encoder 20 may form a residual video block by subtracting pixel values of the predictive block from the pixel values of the current video block being coded, forming pixel difference values. The pixel difference values forming the residual video block may include both luma and chroma component differences. [0096] The intra prediction processing unit 46 may intra-predict a current video block, as an alternative to the inter-prediction performed by the motion estimation unit 42 and the motion compensation unit 44, or the intra block copy prediction performed by the intra BC unit 48, as described above. In particular, the intra prediction processing unit 46 may determine an intra prediction mode to use to encode a current block. To do so, the intra prediction processing unit 46 may encode a current block using various intra prediction modes, e.g., during separate encoding passes, and the intra prediction processing unit 46 (or a mode selection unit, in some examples) may select an appropriate intra prediction mode to use from the tested intra prediction modes. The intra prediction processing unit 46 may provide information indicative of the selected intra- prediction mode for the block to the entropy encoding unit 56. The entropy encoding unit 56 may encode the information indicating the selected intra-prediction mode in the bitstream. [0097] After the prediction processing unit 41 determines the predictive block for the current video block via either inter prediction or intra prediction, the summer 50 forms a residual video block by subtracting the predictive block from the current video block. The residual video data in the residual block may be included in one or more TUs and is provided to the transform processing unit 52. The transform processing unit 52 transforms the residual video data into residual transform coefficients using a transform, such as a Discrete Cosine Transform (DCT) or a conceptually similar transform. [0098] The transform processing unit 52 may send the resulting transform coefficients to the quantization unit 54. The quantization unit 54 quantizes the transform coefficients to further reduce the bit rate. The quantization process may also reduce the bit depth associated with some or all of Attorney Ref.: 186015.20176 the coefficients. The degree of quantization may be modified by adjusting a quantization parameter. In some examples, the quantization unit 54 may then perform a scan of a matrix including the quantized transform coefficients. Alternatively, the entropy encoding unit 56 may perform the scan. [0099] Following quantization, the entropy encoding unit 56 entropy encodes the quantized transform coefficients into a video bitstream using, e.g., Context Adaptive Variable Length Coding (CAVLC), Context Adaptive Binary Arithmetic Coding (CABAC), Syntax-based context- adaptive Binary Arithmetic Coding (SBAC), Probability Interval Partitioning Entropy (PIPE) coding or another entropy encoding methodology or technique. The encoded bitstream may then be transmitted to the video decoder 30 as shown in FIG.1, or archived in the storage device 32 as shown in FIG. 1 for later transmission to or retrieval by the video decoder 30. The entropy encoding unit 56 may also entropy encode the motion vectors and the other syntax elements for the current video frame being coded. [00100] The inverse quantization unit 58 and the inverse transform processing unit 60 apply inverse quantization and inverse transformation, respectively, to reconstruct the residual video block in the pixel domain for generating a reference block for prediction of other video blocks. As noted above, the motion compensation unit 44 may generate a motion compensated predictive block from one or more reference blocks of the frames stored in the DPB 64. The motion compensation unit 44 may also apply one or more interpolation filters to the predictive block to calculate sub-integer pixel values for use in motion estimation. [00101] The summer 62 adds the reconstructed residual block to the motion compensated predictive block produced by the motion compensation unit 44 to produce a reference block for storage in the DPB 64. The reference block may then be used by the intra BC unit 48, the motion estimation unit 42 and the motion compensation unit 44 as a predictive block to inter predict another video block in a subsequent video frame. [00102] Fig.3 is a block diagram illustrating an exemplary video decoder 30 in accordance with some implementations of the present application. The video decoder 30 includes a video data memory 79, an entropy decoding unit 80, a prediction processing unit 81, an inverse quantization unit 86, an inverse transform processing unit 88, a summer 90, and a DPB 92. The prediction processing unit 81 further includes a motion compensation unit 82, an intra prediction unit 84, and an intra BC unit 85. The video decoder 30 may perform a decoding process generally reciprocal Attorney Ref.: 186015.20176 to the encoding process described above with respect to the video encoder 20 in connection with Fig. 2. For example, the motion compensation unit 82 may generate prediction data based on motion vectors received from the entropy decoding unit 80, while the intra-prediction unit 84 may generate prediction data based on intra-prediction mode indicators received from the entropy decoding unit 80. [00103] In some examples, a unit of the video decoder 30 may be tasked to perform the implementations of the present application. Also, in some examples, the implementations of the present disclosure may be divided among one or more of the units of the video decoder 30. For example, the intra BC unit 85 may perform the implementations of the present application, alone, or in combination with other units of the video decoder 30, such as the motion compensation unit 82, the intra prediction unit 84, and the entropy decoding unit 80. In some examples, the video decoder 30 may not include the intra BC unit 85 and the functionality of intra BC unit 85 may be performed by other components of the prediction processing unit 81, such as the motion compensation unit 82. [00104] The video data memory 79 may store video data, such as an encoded video bitstream, to be decoded by the other components of the video decoder 30. The video data stored in the video data memory 79 may be obtained, for example, from the storage device 32, from a local video source, such as a camera, via wired or wireless network communication of video data, or by accessing physical data storage media (e.g., a flash drive or hard disk). The video data memory 79 may include a Coded Picture Buffer (CPB) that stores encoded video data from an encoded video bitstream. The DPB 92 of the video decoder 30 stores reference video data for use in decoding video data by the video decoder 30 (e.g., in intra or inter predictive coding modes). The video data memory 79 and the DPB 92 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including Synchronous DRAM (SDRAM), Magneto-resistive RAM (MRAM), Resistive RAM (RRAM), or other types of memory devices. For illustrative purpose, the video data memory 79 and the DPB 92 are depicted as two distinct components of the video decoder 30 in Fig.3. But it will be apparent to one skilled in the art that the video data memory 79 and the DPB 92 may be provided by the same memory device or separate memory devices. In some examples, the video data memory 79 may be on-chip with other components of the video decoder 30, or off-chip relative to those components. Attorney Ref.: 186015.20176 [00105] During the decoding process, the video decoder 30 receives an encoded video bitstream that represents video blocks of an encoded video frame and associated syntax elements. The video decoder 30 may receive the syntax elements at the video frame level and/or the video block level. The entropy decoding unit 80 of the video decoder 30 entropy decodes the bitstream to generate quantized coefficients, motion vectors or intra-prediction mode indicators, and other syntax elements. The entropy decoding unit 80 then forwards the motion vectors or intra-prediction mode indicators and other syntax elements to the prediction processing unit 81. [00106] When the video frame is coded as an intra predictive coded (I) frame or for intra coded predictive blocks in other types of frames, the intra prediction unit 84 of the prediction processing unit 81 may generate prediction data for a video block of the current video frame based on a signaled intra prediction mode and reference data from previously decoded blocks of the current frame. [00107] When the video frame is coded as an inter-predictive coded (i.e., B or P) frame, the motion compensation unit 82 of the prediction processing unit 81 produces one or more predictive blocks for a video block of the current video frame based on the motion vectors and other syntax elements received from the entropy decoding unit 80. Each of the predictive blocks may be produced from a reference frame within one of the reference frame lists. The video decoder 30 may construct the reference frame lists, List 0 and List 1, using default construction techniques based on reference frames stored in the DPB 92. [00108] In some examples, when the video block is coded according to the intra BC mode described herein, the intra BC unit 85 of the prediction processing unit 81 produces predictive blocks for the current video block based on block vectors and other syntax elements received from the entropy decoding unit 80. The predictive blocks may be within a reconstructed region of the same picture as the current video block defined by the video encoder 20. [00109] The motion compensation unit 82 and/or the intra BC unit 85 determines prediction information for a video block of the current video frame by parsing the motion vectors and other syntax elements, and then uses the prediction information to produce the predictive blocks for the current video block being decoded. For example, the motion compensation unit 82 uses some of the received syntax elements to determine a prediction mode (e.g., intra or inter prediction) used to code video blocks of the video frame, an inter prediction frame type (e.g., B or P), construction information for one or more of the reference frame lists for the frame, motion vectors for each inter Attorney Ref.: 186015.20176 predictive encoded video block of the frame, inter prediction status for each inter predictive coded video block of the frame, and other information to decode the video blocks in the current video frame. [00110] Similarly, the intra BC unit 85 may use some of the received syntax elements, e.g., a flag, to determine that the current video block was predicted using the intra BC mode, construction information of which video blocks of the frame are within the reconstructed region and should be stored in the DPB 92, block vectors for each intra BC predicted video block of the frame, intra BC prediction status for each intra BC predicted video block of the frame, and other information to decode the video blocks in the current video frame. [00111] The motion compensation unit 82 may also perform interpolation using the interpolation filters as used by the video encoder 20 during encoding of the video blocks to calculate interpolated values for sub-integer pixels of reference blocks. In this case, the motion compensation unit 82 may determine the interpolation filters used by the video encoder 20 from the received syntax elements and use the interpolation filters to produce predictive blocks. [00112] The inverse quantization unit 86 inverse quantizes the quantized transform coefficients provided in the bitstream and entropy decoded by the entropy decoding unit 80 using the same quantization parameter calculated by the video encoder 20 for each video block in the video frame to determine a degree of quantization. The inverse transform processing unit 88 applies an inverse transform, e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process, to the transform coefficients in order to reconstruct the residual blocks in the pixel domain. [00113] After the motion compensation unit 82 or the intra BC unit 85 generates the predictive block for the current video block based on the vectors and other syntax elements, the summer 90 reconstructs decoded video block for the current video block by summing the residual block from the inverse transform processing unit 88 and a corresponding predictive block generated by the motion compensation unit 82 and the intra BC unit 85. An in-loop filter 91 such as deblocking filter, SAO filter and/or ALF may be positioned between the summer 90 and the DPB 92 to further process the decoded video block. In some examples, the in-loop filter 91 may be omitted, and the decoded video block may be directly provided by the summer 90 to the DPB 92. The decoded video blocks in a given frame are then stored in the DPB 92, which stores reference frames used for subsequent motion compensation of next video blocks. The DPB 92, or Attorney Ref.: 186015.20176 a memory device separate from the DPB 92, may also store decoded video for later presentation on a display device, such as the display device 34 of Fig.1. [00114] In a typical video coding process, a video sequence typically includes an ordered set of frames or pictures. Each frame may include three sample arrays, denoted SL, SCb, and SCr. SL is a two-dimensional array of luma samples. SCb is a two-dimensional array of Cb chroma samples. SCr is a two-dimensional array of Cr chroma samples. In other instances, a frame may be monochrome and therefore includes only one two-dimensional array of luma samples. [00115] As shown in Fig.4A, the video encoder 20 (or more specifically the partition unit 45) generates an encoded representation of a frame by first partitioning the frame into a set of CTUs. A video frame may include an integer number of CTUs ordered consecutively in a raster scan order from left to right and from top to bottom. Each CTU is a largest logical coding unit and the width and height of the CTU are signaled by the video encoder 20 in a sequence parameter set, such that all the CTUs in a video sequence have the same size being one of 128×128, 64×64, 32×32, and 16×16. But it should be noted that the present application is not necessarily limited to a particular size. As shown in Fig.4B, each CTU may comprise one CTB of luma samples, two corresponding coding tree blocks of chroma samples, and syntax elements used to code the samples of the coding tree blocks. The syntax elements describe properties of different types of units of a coded block of pixels and how the video sequence can be reconstructed at the video decoder 30, including inter or intra prediction, intra prediction mode, motion vectors, and other parameters. In monochrome pictures or pictures having three separate color planes, a CTU may comprise a single coding tree block and syntax elements used to code the samples of the coding tree block. A coding tree block may be an NxN block of samples. [00116] To achieve a better performance, the video encoder 20 may recursively perform tree partitioning such as binary-tree partitioning, ternary-tree partitioning, quad-tree partitioning or a combination thereof on the coding tree blocks of the CTU and divide the CTU into smaller CUs. As depicted in Fig. 4C, the 64x64 CTU 400 is first divided into four smaller CUs, each having a block size of 32x32. Among the four smaller CUs, CU 410 and CU 420 are each divided into four CUs of 16x16 by block size. The two 16x16 CUs 430 and 440 are each further divided into four CUs of 8x8 by block size. Fig.4D depicts a quad-tree data structure illustrating the end result of the partition process of the CTU 400 as depicted in Fig.4C, each leaf node of the quad- tree corresponding to one CU of a respective size ranging from 32x32 to 8x8. Like the CTU Attorney Ref.: 186015.20176 depicted in Fig.4B, each CU may comprise a CB of luma samples and two corresponding coding blocks of chroma samples of a frame of the same size, and syntax elements used to code the samples of the coding blocks. In monochrome pictures or pictures having three separate color planes, a CU may comprise a single coding block and syntax structures used to code the samples of the coding block. It should be noted that the quad-tree partitioning depicted in FIGS.10 and 11 is only for illustrative purposes and one CTU can be split into CUs to adapt to varying local characteristics based on quad/ternary/binary-tree partitions. In the multi-type tree structure, one CTU is partitioned by a quad-tree structure and each quad-tree leaf CU can be further partitioned by a binary and ternary tree structure. As shown in Fig. 4E, there are five possible partitioning types of a coding block having a width W and a height H, i.e., quaternary partitioning, horizontal binary partitioning, vertical binary partitioning, horizontal ternary partitioning, and vertical ternary partitioning. [00117] In some implementations, the video encoder 20 may further partition a coding block of a CU into one or more MxN PBs. A PB is a rectangular (square or non-square) block of samples on which the same prediction, inter or intra, is applied. A PU of a CU may comprise a PB of luma samples, two corresponding PBs of chroma samples, and syntax elements used to predict the PBs. In monochrome pictures or pictures having three separate color planes, a PU may comprise a single PB and syntax structures used to predict the PB. The video encoder 20 may generate predictive luma, Cb, and Cr blocks for luma, Cb, and Cr PBs of each PU of the CU. [00118] The video encoder 20 may use intra prediction or inter prediction to generate the predictive blocks for a PU. If the video encoder 20 uses intra prediction to generate the predictive blocks of a PU, the video encoder 20 may generate the predictive blocks of the PU based on decoded samples of the frame associated with the PU. If the video encoder 20 uses inter prediction to generate the predictive blocks of a PU, the video encoder 20 may generate the predictive blocks of the PU based on decoded samples of one or more frames other than the frame associated with the PU. [00119] After the video encoder 20 generates predictive luma, Cb, and Cr blocks for one or more PUs of a CU, the video encoder 20 may generate a luma residual block for the CU by subtracting the CU’s predictive luma blocks from its original luma coding block such that each sample in the CU’s luma residual block indicates a difference between a luma sample in one of the CU's predictive luma blocks and a corresponding sample in the CU's original luma coding Attorney Ref.: 186015.20176 block. Similarly, the video encoder 20 may generate a Cb residual block and a Cr residual block for the CU, respectively, such that each sample in the CU's Cb residual block indicates a difference between a Cb sample in one of the CU's predictive Cb blocks and a corresponding sample in the CU's original Cb coding block and each sample in the CU's Cr residual block may indicate a difference between a Cr sample in one of the CU's predictive Cr blocks and a corresponding sample in the CU's original Cr coding block. [00120] Furthermore, as illustrated in Fig. 4C, the video encoder 20 may use quad-tree partitioning to decompose the luma, Cb, and Cr residual blocks of a CU into one or more luma, Cb, and Cr transform blocks respectively. A transform block is a rectangular (square or non- square) block of samples on which the same transform is applied. A TU of a CU may comprise a transform block of luma samples, two corresponding transform blocks of chroma samples, and syntax elements used to transform the transform block samples. Thus, each TU of a CU may be associated with a luma transform block, a Cb transform block, and a Cr transform block. In some examples, the luma transform block associated with the TU may be a sub-block of the CU's luma residual block. The Cb transform block may be a sub-block of the CU's Cb residual block. The Cr transform block may be a sub-block of the CU's Cr residual block. In monochrome pictures or pictures having three separate color planes, a TU may comprise a single transform block and syntax structures used to transform the samples of the transform block. [00121] The video encoder 20 may apply one or more transforms to a luma transform block of a TU to generate a luma coefficient block for the TU. A coefficient block may be a two- dimensional array of transform coefficients. A transform coefficient may be a scalar quantity. The video encoder 20 may apply one or more transforms to a Cb transform block of a TU to generate a Cb coefficient block for the TU. The video encoder 20 may apply one or more transforms to a Cr transform block of a TU to generate a Cr coefficient block for the TU. [00122] After generating a coefficient block (e.g., a luma coefficient block, a Cb coefficient block or a Cr coefficient block), the video encoder 20 may quantize the coefficient block. Quantization generally refers to a process in which transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients, providing further compression. After the video encoder 20 quantizes a coefficient block, the video encoder 20 may entropy encode syntax elements indicating the quantized transform coefficients. For example, the video encoder 20 may perform CABAC on the syntax elements indicating the quantized transform Attorney Ref.: 186015.20176 coefficients. Finally, the video encoder 20 may output a bitstream that includes a sequence of bits that forms a representation of coded frames and associated data, which is either saved in the storage device 32 or transmitted to the destination device 14. [00123] After receiving a bitstream generated by the video encoder 20, the video decoder 30 may parse the bitstream to obtain syntax elements from the bitstream. The video decoder 30 may reconstruct the frames of the video data based at least in part on the syntax elements obtained from the bitstream. The process of reconstructing the video data is generally reciprocal to the encoding process performed by the video encoder 20. For example, the video decoder 30 may perform inverse transforms on the coefficient blocks associated with TUs of a current CU to reconstruct residual blocks associated with the TUs of the current CU. The video decoder 30 also reconstructs the coding blocks of the current CU by adding the samples of the predictive blocks for PUs of the current CU to corresponding samples of the transform blocks of the TUs of the current CU. After reconstructing the coding blocks for each CU of a frame, video decoder 30 may reconstruct the frame. [00124] As noted above, video coding achieves video compression using primarily two modes, i.e., intra-frame prediction (or intra-prediction) and inter-frame prediction (or inter- prediction). It is noted that IBC could be regarded as either intra-frame prediction or a third mode. Between the two modes, inter-frame prediction contributes more to the coding efficiency than intra-frame prediction because of the use of motion vectors for predicting a current video block from a reference video block. [00125] But with the ever-improving video data capturing technology and more refined video block size for preserving details in the video data, the amount of data required for representing motion vectors for a current frame also increases substantially. One way of overcoming this challenge is to benefit from the fact that not only a group of neighboring CUs in both the spatial and temporal domains have similar video data for predicting purpose but the motion vectors between these neighboring CUs are also similar. Therefore, it is possible to use the motion information of spatially neighboring CUs and/or temporally co-located CUs as an approximation of the motion information (e.g., motion vector) of a current CU by exploring their spatial and temporal correlation, which is also referred to as “Motion Vector Predictor (MVP)” of the current CU. Attorney Ref.: 186015.20176 [00126] Instead of encoding, into the video bitstream, an actual motion vector of the current CU determined by the motion estimation unit 42 as described above in connection with Fig.2, the motion vector predictor of the current CU is subtracted from the actual motion vector of the current CU to produce a Motion Vector Difference (MVD) for the current CU. By doing so, there is no need to encode the motion vector determined by the motion estimation unit 42 for each CU of a frame into the video bitstream and the amount of data used for representing motion information in the video bitstream can be significantly decreased. [00127] Like the process of choosing a predictive block in a reference frame during inter- frame prediction of a code block, a set of rules need to be adopted by both the video encoder 20 and the video decoder 30 for constructing a motion vector candidate list (also known as a “merge list”) for a current CU using those potential candidate motion vectors associated with spatially neighboring CUs and/or temporally co-located CUs of the current CU and then selecting one member from the motion vector candidate list as a motion vector predictor for the current CU. By doing so, there is no need to transmit the motion vector candidate list itself from the video encoder 20 to the video decoder 30 and an index of the selected motion vector predictor within the motion vector candidate list is sufficient for the video encoder 20 and the video decoder 30 to use the same motion vector predictor within the motion vector candidate list for encoding and decoding the current CU. [00128] Although ALF has been improved in ECM, there is room to further improve its performance. First, an online ALF filter in ECM takes spatial neighboring pixels, fixed ALF filter results and spatial neighboring pixels before deblocking filter as input. Other information such as spatial neighboring pixels in prediction signal, spatial neighboring pixels in residual signal, or spatial neighboring pixels before SAO can also be used as an input to the online ALF filter equation, which may benefit the coding performance. [00129] Second, edge based classifiers and band based classifiers are used adaptively for the online ALF filter in ECM. However, these two classifiers may be further combined to provide other classifiers, which may benefit the coding performance. [00130] Third, the filter shape for the chroma ALF is a diamond filter shape in ECM, while the filter shape for luma ALF is long cross shape, such non-unified design may not be optimal from standardization point of view. Attorney Ref.: 186015.20176 [00131] Fourth, the edge based classifier and the band based classifier in the ECM only consider the pixel values after SAO. However, after the pixel values before the deblocking filter, prediction signal, residual signal, or before SAO are saved as inputs to the online ALF filter equation, these pixel values can also be utilized to design new classifiers, which may benefit the coding performance. [00132] Fifth, the edge based classifier and band based classifier in ECM only considers luma pixel values after SAO. However, the chroma pixel values can also be utilized to design a new classifier, which may benefit the coding performance. [00133] Sixth, similar to the luma pixel values in before deblocking filter, prediction signal, residual signal, or before SAO are saved as additional online luma ALF filter equation input, the chroma pixel values in before deblocking filter, prediction signal, residual signal, or before SAO can also be saved as additional online chroma ALF filter equation input, which may benefit the coding performance. [00134] Seventh, similar to the luma pixel values in before deblocking filter, prediction signal, residual signal, or before SAO are saved as additional online luma ALF filter equation input, the luma pixel values in before deblocking filter, prediction signal, residual signal, or before SAO can also be saved as additional CCALF filter equation input, which may benefit the coding performance. [00135] Eighth, the classifiers design in ECM only considers the reconstruction pixel values. However, the coding mode information such as whether a coding block is coded with skip mode, whether the coding block is coded with intra, inter P or inter B mode can also be utilized to design classifier, which may benefit the coding performance. [00136] To address the issues, the following methods are provided to further improve the existing design of the ALF. In general, the main features of the proposed technologies in this disclosure are summarized as follows: (1) Online ALF filter takes spatial neighboring pixels in prediction signal, spatial neighboring pixels in residual signal, or spatial neighboring pixels before SAO as additional input; (2) The classifiers which combine the features of edge based classifier and band based classifier are used as additional classifier for online ALF filter; (3) The filter shape for chroma ALF is changed from diamond shape to long cross shape to unify with the filter shape for luma ALF; (4) The classifiers which utilize the pixel values in before deblocking filter, prediction signal, residual signal or before SAO are used as additional classifier for online ALF Attorney Ref.: 186015.20176 filter; (5) The classifiers which utilize the chroma pixel values are used as additional classifier for online ALF filter; (6) Online chroma ALF filter takes spatial neighboring pixels in chroma prediction signal, spatial neighboring pixels in chroma residual signal, spatial neighboring pixels before chroma SAO, or spatial neighboring pixels before chroma deblocking as additional input; (7) CCALF filter takes spatial neighboring pixels in luma prediction signal, spatial neighboring pixels in luma residual signal, spatial neighboring pixels before luma SAO, or spatial neighboring pixels before luma deblocking as additional input; and (8) the classifiers which utilize the coding mode information such as whether a coding block is coded with skip mode, whether the coding block is coded with intra, inter P or inter B mode are used as additional classifiers for online ALF filter. It is noted that the disclosed methods may be applied independently or jointly. Information in prediction, residual or before SAO used as additional ALF input [00137] According to the one or more embodiments of the disclosure, information in prediction, residual or before SAO are used as additional ALF equation input. Different methods may be used to achieve this goal. [00138] In the first method, it is proposed to take the spatial neighboring pixels in prediction signal as additional ALF equation input. Various filter shapes can be used to extract the information in prediction signal. For example, the filter shape can be 1×1, 3×3 or 5×5 as shown in FIG 12. Various equation forms can be used to extract the information in prediction signal. In one example, the clipping differences between the surrounding pixels in prediction signal and current pixel are used as ALF equation input. In another example, the clipping differences between the surrounding pixels in prediction signal and the collocated pixel in prediction signal, the clipping difference between the collocated pixel in prediction signal and current pixel are used as ALF equation input. [00139] In the second method, it is proposed to take the spatial neighboring pixels in residual signal as additional ALF equation input. Various filter shapes can be used to extract the information in residual signal. For example, the filter shape can be 1×1, 3×3 or 5×5 as shown in FIG 12. Various equation forms can be used to extract the information in residual signal. In one example, the clipping results of the collocated pixel in residual signal are used as ALF equation input. Attorney Ref.: 186015.20176 [00140] In the third method, it is proposed to take the spatial neighboring pixels in before SAO signal as additional ALF equation input. Various filter shapes can be used to extract the information in before SAO signal. For example, the filter shape can be 1×1, 3×3 or 5×5 as shown in FIG 12. Various equation forms can be used to extract the information in before SAO signal. In one example, the clipping differences between the surrounding pixels in before SAO signal and current pixel are used as ALF equation input. In another example, the clipping differences between the surrounding pixels in before SAO signal and the collocated pixel in before SAO signal, the clipping difference between the collocated pixel in before SAO signal and current pixel are used as ALF equation input. [00141] In the fourth method, it is proposed to take the information in prediction, residual or before SAO signal as ALF equation input. The utilization method proposed in the first, second and third method can be combined to achieve the fourth method. New classifiers combined the features of edge based classifier and band based classifier [00142] According to the one or more embodiments of the disclosure, the features of edge based classifier and band based classifier are combined to derive new classifiers for online ALF filter. Different methods may be used to achieve this goal. [00143] In the first method, it is proposed to first compute the directionality D of the sub- block of luma component, then the sum of sample values of the sub-block is calculated and it is mapped to the index referring to the band based classifier, and the class index for the sub-block is calculated as ^ = ^ ∗ ^_^ + ^ (17) [00144] where B is the index calculated referring to the band based classifier, ^_^ represents the total number of directionalities D. In one example, for the 2x2 luma block, the directionality D is calculated the same to ^_^ in ECM, and B is calculated as B = (sum * 5) >> (sample bit depth + 2) (18) [00145] In the second method, it is proposed to first compute the activity value A of the sub-block of luma component, then the sum of sample values of the sub-block is calculated and it Attorney Ref.: 186015.20176 is mapped to the index referring to the band based classifier, and the class index for the sub-block is calculated as ^ = ^ ∗ ^_^ + ^ (19) [00146] where B is the index calculated referring to the band based classifier, ^_^ represents the total number of the activity value A. In one example, for the 2x2 luma block, the activity value A is calculated the same to ^^{^} _^ in ECM, and B is calculated as B = (sum * 5) >> (sample bit depth + 2) (20) [00147] In the third method, it is proposed to first compute the index of the sub-block of luma component referring to the edge based classifier, then the sum of sample values of the sub- block is calculated and it is mapped to the index referring to the band based classifier, and the class index for the sub-block is calculated as ^ = ^ ∗ ^_^ + ^ (21) [00148] where B is the index calculated referring to the band based classifier, ^_^ represents the total number of the index calculated referring to the edge based classifier, E is the index calculated referring to the edge based classifier. In one example, for the 2x2 luma block, the index E is calculated the same to ^_^ in ECM, and B is calculated as B = (sum * 2) >> (sample bit depth + 2) (22) Adjust the chroma ALF filter shape to unify with luma ALF filter shape [00149] In the third aspect of this disclosure, it is proposed to change the chroma ALF filter shape from diamond shape to long cross shape as shown in FIG. 13A, which is unified with the luma ALF filter shape. Online ALF filter inputs [0001] FIG.13B shows the online ALF filter inputs where the fixed filter output samples are obtained by feeding the reconstructed samples right after SAO into the offline trained fixed filters. Online ALF filter can take reconstructed samples right prior to SAO, i.e., right before Attorney Ref.: 186015.20176 SAO as additional inputs, or take prediction samples as additional inputs, or take both reconstructed samples right before SAO and prediction samples as additional inputs. As shown in FIG.13B, the various inputs of the online ALF filter may include reconstructed samples right before SAO and prediction samples, in addition to reconstructed samples right after SAO, fixed filter output samples, and reconstructed samples before DBF. Filter shapes applied to prediction samples [0002] FIG.13C shows 1x1 and 3x3 filter shapes that are applied to the prediction samples of the ALF in accordance with some examples of the present disclosure. In some examples, assuming that the prediction samples are used as additional inputs for online ALF filter, a filtered sample is derived as ^^{^ ^^ ^^} ^^{^} = ^ + ^ + ^ + ^^ ^_^^_^ ^ + ^^ + ^ where ^

neighboring chroma sample, associated with a chroma signal, right after SAO and ^⁽^,^⁾; ^_^ indicates the clipped difference between a fixed filter output sample and ^(^,^); ℎ_^,^

the clipped difference between a neighboring chroma sample right, associated with a chroma signal, before DBF and ^(^,^). ^_^,^ is the clipped difference between a neighboring chroma sample, associated with a chroma signal (e.g., a chroma prediction signal), and a current sample ^⁽^, ^⁾. The filter coefficients ^_^, ^ = 0, … N, are signalled. Different filter shapes, for example, 1x1 and 3x3 diamond shapes as shown in FIG.13C, can be used. Attorney Ref.: 186015.20176 [0003] When the reconstructed samples right before SAO are used as additional inputs for online ALF filter, the prediction samples in above equation can be directly replaced with the reconstructed samples right before SAO. New classifiers utilized the pixel values in before deblocking filter [00150] According to the one or more embodiments of the disclosure, the pixel values in before deblocking filter are utilized to derive new classifiers for online ALF filter. Different methods may be used to achieve this goal. [00151] In the first method, it is proposed to first compute the directionality D of the sub- block of luma component, then the sum of difference values between sample in after SAO and collocated sample in before deblocking filter of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (23a) [00152] where ^^^ is the difference index, ^_^ represents the total number of directionalities D. In one example, for the 2x2 luma block, the directionality D is calculated the same to ^_^ in ECM, and ^^^ is calculated as ^^^ = ^^^_^^^ > 0? 2: (^^^_^^^ < 0? 0: 1) (24) [00153] In the second method, it is proposed to first compute the activity value A of the sub-block of luma component, then the sum of difference values between sample in after SAO and collocated sample in before deblocking filter of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (25) [00154] where ^^^ is the difference index, ^_^ represents the total number of the activity value A. In one example, for the 2x2 luma block, the activity value A is calculated the same to ^^{^} _^ in ECM, and ^^^ is calculated as in equation (24). [00155] In the third method, it is proposed to first compute the index of the sub-block of luma component referring to the edge based classifier, then the sum of difference values between Attorney Ref.: 186015.20176 sample in after SAO and collocated sample in before deblocking filter of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (26) [00156] where ^^^ is the difference index, ^_^ represents the total number of the index calculated referring to the edge based classifier, E is the index calculated referring to the edge based classifier. In one example, for the 2x2 luma block, the index E is calculated the same to ^_^ in ECM, and ^^^ is calculated as in equation (24). [00157] In the fourth method, it is proposed to first compute the band index B of the sub- block of luma component, then the sum of difference values between sample in after SAO and collocated sample in before deblocking filter of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (27) [00158] where ^^^ is the difference index, ^_^ represents the total number of the band value. In one example, for the 2x2 luma block, the band index B is calculated as B = (sum * 8) >> (sample bit depth + 2) (28) [00159] and ^^^ is calculated as in equation (24). [00160] In the fifth method, it is proposed to compute the sum of difference values between sample in after SAO and collocated sample in before deblocking filter of the sub-block, then the sum of difference values is mapped to the difference index and the difference index is used as the class index. [00161] In the sixth method, it is proposed to calculate the edged based classifier or band based classifier based on the sample values in before deblocking filter, where the calculation method is same to original edge based classifier or band based classifier calculated based on the sample values after SAO. New classifiers utilized the pixel values in prediction signal Attorney Ref.: 186015.20176 [00162] According to the one or more embodiments of the disclosure, the pixel values in prediction signal are utilized to derive new classifiers for online ALF filter. Different methods may be used to achieve this goal. [00163] In the first method, it is proposed to first compute the directionality D of the sub- block of luma component, then the sum of difference values between sample in after SAO and collocated sample in prediction signal of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (29) [00164] where ^^^ is the difference index, ^_^ represents the total number of directionalities D. In one example, for the 2x2 luma block, the directionality D is calculated the same to ^_^ in ECM, and ^^^ is calculated as ^^^ = ^^^_^^^ > 0? 2: (^^^_^^^ < 0? 0: 1) (30) [00165] In the second method, it is proposed to first compute the activity value A of the sub-block of luma component, then the sum of difference values between sample in after SAO and collocated sample in prediction signal of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (31) [00166] where ^^^ is the difference index, ^_^ represents the total number of the activity value A. In one example, for the 2x2 luma block, the activity value A is calculated the same to ^^{^} _^ in ECM, and ^^^ is calculated as in equation (30). [00167] In the third method, it is proposed to first compute the index of the sub-block of luma component referring to the edge based classifier, then the sum of difference values between sample in after SAO and collocated sample in prediction signal of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (32) [00168] where ^^^ is the difference index, ^_^ represents the total number of the index calculated referring to the edge based classifier, E is the index calculated referring to the edge Attorney Ref.: 186015.20176 based classifier. In one example, for the 2x2 luma block, the index E is calculated the same to ^_^ in ECM, and ^^^ is calculated as in equation (30). [00169] In the fourth method, it is proposed to first compute the band index B of the sub- block of luma component, then the sum of difference values between sample in after SAO and collocated sample in prediction signal of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (33) [00170] where ^^^ is the difference index, ^_^ represents the total number of the band value. In one example, for the 2x2 luma block, the band index B is calculated as [00171] B = (sum * 8) >> (sample bit depth + 2) (34) [00172] and ^^^ is calculated as in equation (30). [00173] In the fifth method, it is proposed to compute the sum of difference values between sample in after SAO and collocated sample in prediction signal of the sub-block, then the sum of difference values is mapped to the difference index and the difference index is used as the class index. [00174] In the sixth method, it is proposed to calculate the edged based classifier or band based classifier based on the sample values in prediction signal, where the calculation method is same to original edge based classifier or band based classifier calculated based on the sample values after SAO. New classifiers utilized the pixel values in residual signal [00175] According to the one or more embodiments of the disclosure, the pixel values in residual signal are utilized to derive new classifiers for online ALF filter. Different methods may be used to achieve this goal. [00176] In the first method, it is proposed to first compute the directionality D of the sub- block of luma component, then the sum of pixel values in residual signal of the sub-block is calculated and it is mapped to the residual index, and the class index for the sub-block is calculated as Attorney Ref.: 186015.20176 ^ = ^^^^ ∗ ^_^ + ^ (35) [00177] where ^^^^ is the residual index, ^_^ represents the total number of directionalities D. In one example, for the 2x2 luma block, the directionality D is calculated the same to ^_^ in ECM, and ^^^^ is calculated as ^^^^ = ^^^_^^^^ > 0? 2: (^^^_^^^^ < 0? 0: 1) (36) [00178] In the second method, it is proposed to first compute the activity value A of the sub-block of luma component, then the sum of pixel values in residual signal of the sub-block is calculated and it is mapped to the residual index, and the class index for the sub-block is calculated as ^ = ^^^^ ∗ ^_^ + ^ (37) [00179] where ^^^^ is the residual index, ^_^ represents the total number of the activity value A. In one example, for the 2x2 luma block, the activity value A is calculated the same to ^^{^} _^ in ECM, and ^^^^ is calculated as in equation (36). [00180] In the third method, it is proposed to first compute the index of the sub-block of luma component referring to the edge based classifier, then the sum of pixel values in residual signal of the sub-block is calculated and it is mapped to the residual index, and the class index for the sub-block is calculated as ^ = ^^^^ ∗ ^_^ + ^ (38) [00181] where ^^^^ is the residual index, ^_^ represents the total number of the index calculated referring to the edge based classifier, E is the index calculated referring to the edge based classifier. In one example, for the 2x2 luma block, the index E is calculated the same to ^_^ in ECM, and ^^^^ is calculated as in equation (36). [00182] In the fourth method, it is proposed to first compute the band index B of the sub- block of luma component, then the sum of pixel values in residual signal of the sub-block is calculated and it is mapped to the residual index, and the class index for the sub-block is calculated as ^ = ^^^^ ∗ ^_^ + ^ (39) Attorney Ref.: 186015.20176 [00183] where ^^^^ is the residual index, ^_^ represents the total number of the band value. In one example, for the 2x2 luma block, the band index B is calculated as B = (sum * 8) >> (sample bit depth + 2) (40) [00184] and ^^^^ is calculated as in equation (36). [00185] In the fifth method, it is proposed to compute the sum of pixel values in residual signal of the sub-block, then the sum of residual values is mapped to the residual index and the residual index is used as the class index. New classifiers utilized the pixel values in before SAO [00186] According to the one or more embodiments of the disclosure, the pixel values in before SAO are utilized to derive new classifiers for online ALF filter. Different methods may be used to achieve this goal. [00187] In the first method, it is proposed to first compute the directionality D of the sub- block of luma component, then the sum of difference values between sample in after SAO and collocated sample in before SAO of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (41) where ^^^ is the difference index, ^_^ represents the total number of directionalities D. In one example, for the 2x2 luma block, the directionality D is calculated the same to ^_^ in ECM, and ^^^ is calculated as ^^^ = ^^^_^^^ > 0? 2: (^^^_^^^ < 0? 0: 1) (42) [00188] In the second method, it is proposed to first compute the activity value A of the sub-block of luma component, then the sum of difference values between sample in after SAO and collocated sample in before SAO of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (43) Attorney Ref.: 186015.20176 [00189] where ^^^ is the difference index, ^_^ represents the total number of the activity value A. In one example, for the 2x2 luma block, the activity value A is calculated the same to ^^{^} _^ in ECM, and ^^^ is calculated as in equation (42). [00190] In the third method, it is proposed to first compute the index of the sub-block of luma component referring to the edge based classifier, then the sum of difference values between sample in after SAO and collocated sample in before SAO of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (44) [00191] where ^^^ is the difference index, ^_^ represents the total number of the index calculated referring to the edge based classifier, E is the index calculated referring to the edge based classifier. In one example, for the 2x2 luma block, the index E is calculated the same to ^_^ in ECM, and ^^^ is calculated as in equation (42). [00192] In the fourth method, it is proposed to first compute the band index B of the sub- block of luma component, then the sum of difference values between sample in after SAO and collocated sample in before SAO of the sub-block is calculated and it is mapped to the difference index, and the class index for the sub-block is calculated as ^ = ^^^ ∗ ^_^ + ^ (45) [00193] where ^^^ is the difference index, ^_^ represents the total number of the band value. In one example, for the 2x2 luma block, the band index B is calculated as B = (sum * 8) >> (sample bit depth + 2) (46) [00194] and ^^^ is calculated as in equation (42). [00195] In the fifth method, it is proposed to compute the sum of difference values between sample in after SAO and collocated sample in before SAO of the sub-block, then the sum of difference values is mapped to the difference index and the difference index is used as the class index. [00196] In the sixth method, it is proposed to calculate the edged based classifier or band based classifier based on the sample values in before SAO, where the calculation method is same Attorney Ref.: 186015.20176 to original edge based classifier or band based classifier calculated based on the sample values after SAO. New classifiers utilized chroma pixel values [00197] According to the one or more embodiments of the disclosure, the chroma pixel values are utilized to derive new classifiers for online ALF filter. Different methods may be used to achieve this goal. [00198] In the first method, it is proposed to first compute the band index ^_^ of the sub- block of luma component, then the band index ^_^ and ^_^ of the corresponding U and V components are computed, and the class index for the sub-block is calculated as ^ = ^_^ ∗ ^_^ ∗ ^_^ + ^_^ ∗ ^_^ + ^_^ (47) [00199] where ^_^, ^_^ and ^_^ are the Y , U and V index calculated referring to the band based classifier, ^_^ and ^_^ represent the total number of the U and V band index value. In one example, for the 2x2 luma block, the ^_^, ^_^ and ^_^ are calculated as ^_^ = (sumY * 6) >> (sample bit depth + 2) (48) ^_^ = (sumU * 2) >> (sample bit depth + 2) (49) ^_^ = (sumV * 2) >> (sample bit depth + 2) (50) Chroma information in before deblocking, prediction, residual or before SAO used as additional chroma ALF input [00200] According to the one or more embodiments of the disclosure, chroma information in before deblocking, prediction, residual or before SAO are used as additional chroma ALF equation inputs. Different methods may be used to achieve this goal. [00201] In the first method, it is proposed to take the spatial neighboring pixels in chroma prediction signal as additional chroma ALF equation inputs. Various filter shapes can be used to extract the information in chroma prediction signal. For example, the filter shape can be 1×1, 3×3 or 5×5 as shown in FIG 12. Various equation forms can be used to extract the information in chroma prediction signal. In one example, the clipping differences between the surrounding pixels in chroma prediction signal and current chroma pixel are used as chroma ALF equation inputs. In another example, the clipping differences between the surrounding pixels in chroma prediction Attorney Ref.: 186015.20176 signal and the collocated pixel in chroma prediction signal, the clipping difference between the collocated pixel in chroma prediction signal and current chroma pixel are used as chroma ALF equation inputs. [00202] In the second method, it is proposed to take the spatial neighboring pixels in chroma residual signal as additional chroma ALF equation inputs. Various filter shapes can be used to extract the information in chroma residual signal. For example, the filter shape can be 1×1, 3×3 or 5×5 as shown in FIG 12. Various equation forms can be used to extract the information in chroma residual signal. In one example, the clipping results of the collocated pixel in chroma residual signal are used as chroma ALF equation inputs. [00203] In the third method, it is proposed to take the spatial neighboring pixels in before chroma SAO signal as additional chroma ALF equation inputs. Various filter shapes can be used to extract the information in before chroma SAO signal. For example, the filter shape can be 1×1, 3×3 or 5×5 as shown in FIG 12. Various equation forms can be used to extract the information in before chroma SAO signal. In one example, the clipping differences between the surrounding pixels in before chroma SAO signal and current chroma pixel are used as chroma ALF equation inputs. In another example, the clipping differences between the surrounding pixels in before chroma SAO signal and the collocated pixel in before chroma SAO signal, the clipping difference between the collocated pixel in before chroma SAO signal and current chroma pixel are used as chroma ALF equation inputs. [00204] In the fourth method, it is proposed to take the spatial neighboring pixels in before chroma deblocking signal as additional chroma ALF equation inputs. Various filter shapes can be used to extract the information in before chroma deblocking signal. For example, the filter shape can be 1×1, 3×3 or 5×5 as shown in FIG 12. Various equation forms can be used to extract the information in before chroma deblocking signal. In one example, the clipping differences between the surrounding pixels in before chroma deblocking signal and current chroma pixel are used as chroma ALF equation inputs. In another example, the clipping differences between the surrounding pixels in before chroma deblocking signal and the collocated pixel in before chroma deblocking signal, the clipping difference between the collocated pixel in before chroma deblocking signal and current chroma pixel are used as chroma ALF equation inputs. [00205] In the fifth method, it is proposed to take the information in chroma prediction, residual, before SAO or before deblocking signal as chroma ALF equation inputs. The utilization Attorney Ref.: 186015.20176 method proposed in the first, second third, fourth method can be combined to achieve the fifth method. Luma information in before deblocking, prediction, residual or before SAO used as additional CCALF input [00206] According to the one or more embodiments of the disclosure, luma information in before deblocking, prediction, residual or before SAO are used as additional CCALF equation inputs. Different methods may be used to achieve this goal. [00207] In the first method, it is proposed to take the spatial neighboring pixels in luma prediction signal as additional CCALF equation inputs. Various filter shapes can be used to extract the information in luma prediction signal. For example, the filter shape can be 3x4 as shown in FIG 10. Various equation forms can be used to extract the information in luma prediction signal. In one example, the differences between the surrounding pixels in luma prediction signal and current corresponding luma pixel are used as CCALF equation inputs. In another example, the differences between the surrounding pixels in luma prediction signal and the collocated pixel in current corresponding luma prediction signal, the difference between the collocated pixel in current corresponding luma prediction signal and current corresponding luma pixel are used as CCALF equation inputs. [00208] In the second method, it is proposed to take the spatial neighboring pixels in luma residual signal as additional CCALF equation inputs. Various filter shapes can be used to extract the information in luma residual signal. For example, the filter shape can be 3x4 as shown in FIG 10. Various equation forms can be used to extract the information in luma residual signal. In one or more examples, the collocated pixels in luma residual signal are used as CCALF equation inputs. [00209] In the third method, it is proposed to take the spatial neighboring pixels in before luma SAO signal as additional CCALF equation inputs. Various filter shapes can be used to extract the information in before luma SAO signal. For example, the filter shape can be 3x4 as shown in FIG 10. Various equation forms can be used to extract the information in before luma SAO signal. In one example, the differences between the surrounding pixels in before luma SAO signal and current corresponding luma pixel are used as CCALF equation inputs. In another example, the differences between the surrounding pixels in before luma SAO signal and the collocated pixel in Attorney Ref.: 186015.20176 current corresponding before luma SAO signal, the difference between the collocated pixel in current corresponding before luma SAO signal and current corresponding luma pixel are used as CCALF equation inputs. [00210] In the fourth method, it is proposed to take the spatial neighboring pixels in before luma deblocking signal as additional CCALF equation inputs. Various filter shapes can be used to extract the information in before luma deblocking signal. For example, the filter shape can be 3x4 as shown in FIG 10. Various equation forms can be used to extract the information in before luma deblocking signal. In one example, the differences between the surrounding pixels in before luma deblocking signal and current corresponding luma pixel are used as CCALF equation inputs. In another example, the differences between the surrounding pixels in before luma deblocking signal and the collocated pixel in current corresponding before luma deblocking signal, the difference between the collocated pixel in current corresponding before luma deblocking signal and current corresponding luma pixel are used as CCALF equation inputs. [00211] In the fifth method, it is proposed to take the information in luma prediction, residual, before SAO or before deblocking signal as CCALF equation inputs. The utilization method proposed in the first, second third, fourth method can be combined to achieve the fifth method. New classifiers utilized the coding mode information [00212] According to the one or more embodiments of the disclosure, the coding mode information such as whether the coding block is coded with skip mode, whether the coding block is coded with intra, inter P or inter B mode, is utilized to derive new classifiers for online ALF filter. Different methods may be used to achieve this goal. [00213] In the first method, it is proposed to record whether the coding block is coded with skip mode during the encoding and decoding process, then this information is utilized to design a new classifier. In one example, the classifier which has 2 classes corresponding to the skip mode is true or false is added as a new classifier. In another example, the classifier which combines the skip mode information with EO or BO is added as a new classifier. [00214] In the second method, it is proposed to record whether the coding block is coded with intra mode, inter P mode, or inter B mode during the encoding and decoding process, then this information is utilized to design a new classifier. In one example, the classifier which has 3 Attorney Ref.: 186015.20176 classes corresponding to the intra mode, inter P mode or inter B mode is added as a new classifier. In another example, the classifier which combines the intra, inter P or inter B mode information with EO or BO is added as a new classifier. [00215] In the third method, it is proposed to take both the coding mode information whether the coding block is coded with skip mode, whether the coding block is coded with intra, inter P or inter B mode to design the new classifier. The utilization method proposed in the first and second method can be combined to achieve the third method. [00216] FIG.14 is a flowchart illustrating a method 1400 for video decoding in accordance with some examples of the present disclosure. At step 1401, the method 1400 includes obtaining, by a decoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of the following signals: (i) a chroma prediction signal, (ii) a chroma residual signal, (iii) a pre-chroma sample adaptive offset (SAO) signal, or (iv) a pre-chroma deblocking signal. At step 1402, the method 1400 includes obtaining, by the decoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample. [00217] In one example, the method 1400 further includes obtaining, by the decoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the chroma prediction signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00218] In one example, the method 1400 further includes obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the chroma prediction signal and the current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results. [00219] In one example, the method 1400 further includes: obtaining, by the decoder, clipped results based on differences between surrounding samples in the chroma prediction signal and collocated samples in the chroma prediction signal, and clipped results based on differences between collocated samples in chroma prediction signal and current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results. [00220] In one example, the method 1400 further includes: obtaining, by the decoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring Attorney Ref.: 186015.20176 samples associated with the chroma residual signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00221] In one example, the method 1400 further includes: obtaining, by the decoder, clipped results of one or more spatial neighboring samples in the chroma residual signal; and deriving, by the decoder, a chroma ALF input based on the clipped results. [00222] In one example, the method 1400 further includes: obtaining, by the decoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-chroma SAO signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00223] In one example, the method 1400 further includes: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the pre-chroma SAO signal and the current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results. [00224] In one example, the method 1400 further includes: obtaining, by the decoder, clipped results based on differences between surrounding samples from the pre-chroma SAO signal and collocated samples from the pre-chroma SAO signal, and clipped results based on differences between collocated samples in pre-chroma SAO signal and current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results. [00225] In one example, the method 1400 further includes: obtaining, by the decoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-chroma deblocking signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00226] In one example, the method 1400 further includes: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples in the pre- chroma deblocking signal and the current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results. [00227] In one example, the method 1400 further includes: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the pre-chroma deblocking signal and collocated samples from the pre-chroma deblocking signal, and clipped results based on differences between collocated samples in pre-chroma deblocking signal Attorney Ref.: 186015.20176 and current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results. [00228] In one example, the one or more surrounding samples are from a combination of following signals: (i) the chroma prediction signal, (ii) the chroma residual signal, (iii) the pre- chroma sample adaptive offset (SAO) signal, or (iv) the pre-chroma deblocking signal. [00229] FIG.15 is a flowchart illustrating a method 1500 for video encoding in accordance with some examples of the present disclosure. At step 1501, the method 1500 includes obtaining, by an encoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of the following signals: (i) a chroma prediction signal, (ii) a chroma residual signal, (iii) a pre-chroma sample adaptive offset (SAO) signal, of (iv) a pre-chroma deblocking signal. At step 1502, the method 1500 includes obtaining, by the encoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample. [00230] In one example, the method 1500 further includes: obtaining, by the encoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the chroma prediction signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00231] In one example, the method 1500 further includes: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples in the chroma prediction signal and the current chroma sample; and deriving, by the encoder, a chroma ALF input based on the clipped results. [00232] In one example, the method 1500 further includes: obtaining, by the encoder, clipped results based on differences between surrounding samples in the chroma prediction signal and collocated samples in the chroma prediction signal, and clipped results based on differences between collocated samples in chroma prediction signal and current chroma sample; and deriving, by the encoder, a chroma ALFinput based on the clipped results. [00233] In one example, the method 1500 further includes: obtaining, by the encoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the chroma residual signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. Attorney Ref.: 186015.20176 [00234] In one example, the method 1500 further includes: obtaining, by the encoder, clipped results of one or more spatial neighboring samples from the chroma residual signal; and deriving, by the encoder, a chroma ALF input based on the clipped results. [00235] In one example, the method 1500 further includes: obtaining, by the encoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-chroma SAO signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00236] In one example, the method 1500 further includes: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples from the pre-chroma SAO signal and the current chroma sample; and deriving, by the encoder, a chroma ALF input based on the clipped results. [00237] In one example, the method 1500 further includes: obtaining, by the encoder, clipped results based on differences between surrounding samples from the pre-chroma SAO signal and collocated samples from the pre-chroma SAO signal, and clipped results based on differences between collocated samples in pre-chroma SAO signal and current chroma sample; and deriving, by the encoder, a chroma ALF input based on the clipped results. [00238] In one example, the method 1500 further includes: obtaining, by the encoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-chroma deblocking signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00239] In one example, the method 1500 further includes: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples in the pre- chroma deblocking signal and the current chroma sample; and deriving, by the encoder, a chroma ALF input based on the clipped results. [00240] In one example, the method 1500 further includes: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples in the pre- chroma deblocking signal and collocated samples in pre-chroma deblocking signal, and clipped results based on differences between collocated samples in pre-chroma deblocking signal and current chroma sample; and deriving, by the encoder, a chroma ALF input based on the clipped results. Attorney Ref.: 186015.20176 [00241] In one example, the one or more surrounding samples are from a combination of following signals: (i) the chroma prediction signal, (ii) the chroma residual signal, (iii) the pre- chroma SAO signal, or (iv) the pre-chroma deblocking signal. [00242] FIG.16 is a flowchart illustrating a method 1600 for video decoding in accordance with some examples of the present disclosure. At step 1601, the method 1600 includes obtaining, by a decoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of following signals: (i) a luma prediction signal, (ii) a luma residual signal, (iii) a pre-luma sample adaptive offset (SAO) signal, or (iv) a pre-luma deblocking signal. At step 1602, the method 1600 includes obtaining, by the decoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample. [00243] In one example, the method 1600 further includes: obtaining, by the decoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the luma prediction signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00244] In one example, the method 1600 further includes: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the luma prediction signal and the current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. [00245] In one example, the method 1600 further includes: obtaining, by the decoder, clipped results based on differences between surrounding samples in the luma prediction signal and collocated samples in the luma prediction signal, and clipped results based on differences between collocated samples in the luma prediction signal and current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. [00246] In one example, the method 1600 further includes: obtaining, by the decoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the luma residual signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00247] In one example, the method 1600 further includes: obtaining, by the decoder, clipped results of one or more spatial neighboring samples in the luma residual signal; and deriving, by the decoder, the CCALF input based on the clipped results. Attorney Ref.: 186015.20176 [00248] In one example, the method 1600 further includes: obtaining, by the decoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-luma SAO signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00249] In one example, the method 1600 further includes: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples in the pre- luma SAO signal and the current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. [00250] In one example, the method 1600 further includes: obtaining, by the decoder, clipped results based on differences between surrounding samples from the pre-luma SAO signal and collocated samples from the pre-luma SAO signal, and clipped results based on differences between collocated samples in the pre-luma SAO signal and current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. [00251] In one example, the method 1600 further includes: obtaining, by the decoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-luma deblocking signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00252] In one example, the method 1600 further includes: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the pre-luma deblocking signal and the current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. [00253] In one example, the method 1600 further includes: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the pre-luma deblocking signal and collocated samples from the pre-luma deblocking signal, and clipped results based on differences between collocated samples in the pre-luma deblocking signal and current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. [00254] In one example, the neighboring samples are from a combination of following signals: (i) the luma prediction signal; (ii) the luma residual signal; (iii) the pre-luma SAO signal; or (iv) the pre-luma deblocking signal. Attorney Ref.: 186015.20176 [00255] FIG.17 is a flowchart illustrating a method 1700 for video encoding in accordance with some examples of the present disclosure. At step 1701, the method 1700 includes obtaining, by an encoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of following signals: (i) a luma prediction signal, (ii) a luma residual signal, (iii) a pre-luma sample adaptive offset (SAO) signal, or (iv) a pre-luma deblocking signal. At step 1702, the method 1700 includes obtaining, by the encoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample. [00256] In one example, the method 1700 further includes: obtaining, by the encoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the luma prediction signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00257] In one example, the method 1700 further includes: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples from the luma prediction signal and the current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. [00258] In one example, the method 1700 further includes: obtaining, by the encoder, clipped results based on differences between surrounding samples the luma prediction signal and collocated samples in the luma prediction signal, and clipped results based on differences between collocated samples in the luma prediction signal and current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. [00259] In one example, the method 1700 further includes: obtaining, by the encoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the luma residual signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00260] In one example, the method 1700 further includes: obtaining, by the encoder, clipped results of one or more spatial neighboring samples from the luma residual signal; and deriving, by the encoder, the CCALF input based on the clipped results. [00261] In one example, the method 1700 further includes: obtaining, by the encoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more Attorney Ref.: 186015.20176 spatial neighboring samples associated with the pre-luma SAO signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00262] In one example, the method 1700 further includes: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples from the pre-luma SAO signal and the current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. [00263] In one example, the method 1700 further includes: obtaining, by the encoder, clipped results based on differences between surrounding samples from the pre-luma SAO signal and collocated samples from the pre-luma SAO signal, and clipped results based on differences between collocated samples in the pre-luma SAO signal and current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. [00264] In one example, the method 1700 further includes: obtaining, by the encoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-luma deblocking signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. [00265] In one example, the method 1700 further includes: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples from the pre-luma deblocking signal and the current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. [00266] In one example, the method 1700 further includes: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples from the pre-luma deblocking signal and collocated samples from the pre-luma deblocking signal, and clipped results based on differences between collocated samples in the pre-luma deblocking signal and current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. [00267] In one example, the one or more spatial neighboring samples are from a combination of following signals: (i) the luma prediction signal; (ii) the luma residual signal; (iii) the pre-luma SAO signal; or (iv)the pre-luma deblocking signal. [00268] FIG.18 is a flowchart illustrating a method 1800 for video decoding in accordance with some examples of the present disclosure. At step 1801, the method 1800 includes obtaining, by a decoder, coding information associated with a coding block, wherein the coding information Attorney Ref.: 186015.20176 includes a first flag indicating that the coding block is coded with a skip mode and a second flag indicating that the coding block is coded with at least one of the following modes: an intra mode, an inter P mode, or an inter B mode, to derive new classifiers for an online adaptive loop filter (ALF) process. At step 1802, the method 1800 includes generating, by the decoder, a new classifier for the online adaptive ALF process based on the coding information. [00269] In one example, the method 1800 further includes using the first flag to derive the new classifier for the online ALF process. [00270] In one example, the new classifier includes two classes corresponding to whether the coding block is coded with the skip mode. [00271] In one example, the new classifier combines skip mode information with at least one of: edge offset(EO) (edge-based classifier) information, or band offset (BO) (band-based classifier) information. [00272] In one example, the method 1800 further includes: recording, at the decoder, that the coding block is coded with at least one of following modes: (i) intra mode, (ii) inter P mode, or (iii) inter B mode; and generating, at the decoder, the new classifier for the online ALF process based on the recording. [00273] In one example, the new classifier includes three classes corresponding to the coding block is coded with intra mode, inter P mode, or inter B mode. [00274] In one example, the new classifier combines: information that the coding block is coded with at least one of: intra mode, inter P mode, or inter B mode, with at least one of: edge offset (EO) (edge based classifier) information, or band offset(BO) (band based classifier) information. [00275] In one example, the method 1800 further includes: determining, at the decoder, that whether the coding block is coded with skip mode; determining, at the decoder, that the coding block is coded with one of the following modes: (i) intra mode; (ii) inter P mode; or (iii) inter B mode; and generating, at the decoder, the new classifier based on the determined modes. [00276] FIG.19 is a flowchart illustrating a method 1900 for video encoding in accordance with some examples of the present disclosure. At step 1901, the method 1900 includes obtaining, by an encoder, coding information associated with a coding block, wherein the coding information includes information whether the coding block is coded with a skip mode and information that the coding block is coded with at least one of the following: an intra mode, an inter P mode, or an inter Attorney Ref.: 186015.20176 B mode, to derive new classifiers for an online adaptive loop filter (ALF) process. At step 1902, the method 1900 includes generating, by the encoder, a new classifier for the online ALF process based on the coding information. [00277] In one example, the coding block is coded with the skip mode during an encoding process is utilized to derive the new classifier for the online ALF process. [00278] In one example, the new classifier includes two classes corresponding to whether the coding block is coded with the skip mode. [00279] In one example, the new classifier combines skip mode information with edge offset (EO) (edge based classifier) information or band offset(BO) (band based classifier) information. [00280] In one example, the method 1900 includes recording, at the encoder, that the coding block is coded with at least one of: (i) intra mode, (ii) inter P mode, or (iii) inter B mode; and generating, by the encoder, the new classifier for the online ALF process based on the recording. [00281] In one example, the new classifier includes three classes corresponding to the coding block is coded with intra mode, inter P mode, or inter B mode. [00282] In one example, the new classifier combines: information that the coding block is coded with at least one of: intra mode, inter P mode, or inter B mode, with at least one of: edge offset (EO) (edge based classifier) information, or (BO) (band based classifier) information. [00283] In one example, the method 1900 further includes: determining, at the encoder, whether the coding block is coded with skip mode; determining, at the encoder, that the coding block is coded with one of the following modes: (i) intra mode; (ii) inter P mode; or (iv) inter B mode; and generating the new classifier based on the modes. [00284] FIG.20 shows a computing environment 2010 coupled with a user interface 2050. The computing environment 2010 can be part of a data processing server. The computing environment 2010 includes a processor 2020, a memory 2030, and an Input/Output (I/O) interface 2040. [00285] The processor 2020 typically controls overall operations of the computing environment 2010, such as the operations associated with display, data acquisition, data communications, and image processing. The processor 2020 may include one or more processors to execute instructions to perform all or some of the steps in the above-described methods. Attorney Ref.: 186015.20176 Moreover, the processor 2020 may include one or more modules that facilitate the interaction between the processor 2020 and other components. The processor may be a Central Processing Unit (CPU), a microprocessor, a single chip machine, a Graphical Processing Unit (GPU), or the like. [00286] The memory 2030 is configured to store various types of data to support the operation of the computing environment 2010. The memory 2030 may include predetermined software 2032. Embodiments of such data includes instructions for any applications or methods operated on the computing environment 2010, video datasets, image data, etc. The memory 2030 may be implemented by using any type of volatile or non-volatile memory devices, or a combination thereof, such as a Static Random Access Memory (SRAM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), an Erasable Programmable Read-Only Memory (EPROM), a Programmable Read-Only Memory (PROM), a Read-Only Memory (ROM), a magnetic memory, a flash memory, a magnetic or optical disk. [00287] In one example, the memory 2030 is configured to store instructions executable by the processor; where the processor, upon execution of the instructions, is configured to perform any method as illustrated in FIGS.14-19. [00288] The I/O interface 2040 provides an interface between the processor 2020 and peripheral interface modules, such as a keyboard, a click wheel, buttons, and the like. The buttons may include but are not limited to, a home button, a start scan button, and a stop scan button. The I/O interface 2040 can be coupled with an encoder and decoder. [00289] In an embodiment, there is also provided a non-transitory computer-readable storage medium comprising a plurality of programs, for example, in the memory 2030, executable by the processor 2020 in the computing environment 2010, for performing the above-described methods. Alternatively, the non-transitory computer-readable storage medium may have stored therein a bitstream or a data stream comprising encoded video information (for example, video information comprising one or more syntax elements) generated by an encoder (for example, the Attorney Ref.: 186015.20176 video encoder 20 in Fig.2) using, for example, the encoding method described above for use by a decoder (for example, the video decoder 30 in Fig.3) in decoding video data. The non-transitory computer-readable storage medium may be, for example, a ROM, a Random Access Memory (RAM), a CD-ROM, a magnetic tape, a floppy disc, an optical data storage device or the like. [00290] In an embodiment, the is also provided a computing device comprising one or more processors (for example, the processor 2020); and the non-transitory computer-readable storage medium or the memory 2030 having stored therein a plurality of programs executable by the one or more processors, wherein the one or more processors, upon execution of the plurality of programs, are configured to perform the above-described methods. [00291] In an embodiment, there is also provided a computer program product comprising a plurality of programs, for example, in the memory 2030, executable by the processor 2020 in the computing environment 2010, for performing the above-described methods. For example, the computer program product may include the non-transitory computer-readable storage medium. [00292] In an embodiment, the computing environment 2010 may be implemented with one or more ASICs, DSPs, Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), FPGAs, GPUs, controllers, micro-controllers, microprocessors, or other electronic components, for performing the above methods. [00293] The description of the present disclosure has been presented for purposes of illustration and is not intended to be exhaustive or limited to the present disclosure. Many modifications, variations, and alternative implementations will be apparent to those of ordinary skill in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. [00294] Unless specifically stated otherwise, an order of steps of the method according to the present disclosure is only intended to be illustrative, and the steps of the method according to the present disclosure are not limited to the order specifically described above, but may be changed Attorney Ref.: 186015.20176 according to practical conditions. In addition, at least one of the steps of the method according to the present disclosure may be adjusted, combined or deleted according to practical requirements. [00295] The embodiments were chosen and described in order to explain the principles of the disclosure and to enable others skilled in the art to understand the disclosure for various implementations and to best utilize the underlying principles and various implementations with various modifications as are suited to the particular use contemplated. Therefore, it is to be understood that the scope of the disclosure is not to be limited to the specific embodiments of the implementations disclosed and that modifications and other implementations are intended to be included within the scope of the present disclosure. [00296] The above methods may be implemented using an apparatus that includes one or more circuitries, which include application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), controllers, micro-controllers, microprocessors, or other electronic components. The apparatus may use the circuitries in combination with the other hardware or software components for performing the above described methods. Each module, sub-module, unit, or sub-unit disclosed above may be implemented at least partially using the one or more circuitries. [00297] Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed here. This application is intended to cover any variations, uses, or adaptations of the disclosure following the general principles thereof and including such departures from the present disclosure as come within known or customary practice in the art. It is intended that the specification and embodiments be considered as exemplary only. The specification and embodiments are considered as exemplary. The application is intended to cover any variations, uses, or adaptations of the disclosure. [00298] It will be appreciated that the present disclosure is not limited to the exact embodiments described above and illustrated in the accompanying drawings, and that various modifications and changes can be made without departing from the scope thereof.

Claims

Attorney Ref.: 186015.20176 WHAT IS CLAIMED IS: 1. A method for video decoding, comprising: obtaining, by a decoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of following signals: (i) a chroma prediction signal, (ii) a chroma residual signal, (iii) a pre- chroma sample adaptive offset (SAO) signal, or (iv) a pre-chroma deblocking signal; and obtaining, by the decoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample. 2. The method for video decoding of claim 1, further comprising: obtaining, by the decoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the chroma prediction signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 3. The method for video decoding of claim 2, further comprising: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the chroma prediction signal and the current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results. 4. The method for video decoding of claim 2, further comprising: obtaining, by the decoder, clipped results based on differences between surrounding samples in the chroma prediction signal and collocated samples in the chroma prediction signal, and clipped results based on differences between collocated samples in chroma prediction signal and current chroma sample; and Attorney Ref.: 186015.20176 deriving, by the decoder, a chroma ALF input based on the clipped results. 5. The method for video decoding of claim 1, further comprising: obtaining, by the decoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the chroma residual signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 6. The method for video decoding of claim 5, further comprising: obtaining, by the decoder, clipped results of one or more spatial neighboring samples in the chroma residual signal; and deriving, by the decoder, a chroma ALF input based on the clipped results. 7. The method for video decoding of claim 1, further comprising: obtaining, by the decoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-chroma SAO signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 8. The method for video decoding of claim 7, further comprising: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the pre-chroma SAO signal and the current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results. 9. The method for video decoding of claim 7, further comprising: Attorney Ref.: 186015.20176 obtaining, by the decoder, clipped results based on differences between surrounding samples from the pre-chroma SAO signal and collocated samples from the pre-chroma SAO signal, and clipped results based on differences between collocated samples in pre-chroma SAO signal and current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results. 10. The method for video decoding of claim 1, further comprising: obtaining, by the decoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-chroma deblocking signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 11. The method for video decoding of claim 10, further comprising: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples in the pre-chroma deblocking signal and the current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results 12. The method for video decoding of claim 10, further comprising: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the pre-chroma deblocking signal and collocated samples from the pre-chroma deblocking signal, and clipped results based on differences between collocated samples in pre-chroma deblocking signal and current chroma sample; and deriving, by the decoder, a chroma ALF input based on the clipped results. Attorney Ref.: 186015.20176 13. The method for video decoding of claim 1, wherein one or more surrounding samples are from a combination of following signals: (i) the chroma prediction signal, (ii) the chroma residual signal, (iii) the pre-chroma sample adaptive offset (SAO) signal, or (iv) the pre-chroma deblocking signal. 14. A method for video encoding, comprising: obtaining, by an encoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from a chroma sample, wherein the one or more spatial neighboring samples are from at least one of following signals: (i) a chroma prediction signal (ii) a chroma residual signal (iii) a pre-chroma sample adaptive offset (SAO) signal, or (iv) a pre-chroma deblocking signal; and obtaining, by the encoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample. 15. The method for video encoding of claim 14, further comprising: obtaining, by the encoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the chroma prediction signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 16. The method for video encoding of claim 15, further comprising: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples in the chroma prediction signal and the current chroma sample; and deriving, by the encoder, a chroma ALF input based on the clipped results. 17. The method for video encoding of claim 15, further comprising: Attorney Ref.: 186015.20176 obtaining, by the encoder, clipped results based on differences between surrounding samples in the chroma prediction signal and collocated samples in the chroma prediction signal, and clipped results based on differences between collocated samples in chroma prediction signal and current chroma sample; and deriving, by the encoder, a chroma ALFinput based on the clipped results. 18. The method for video encoding of claim 14, further comprising: obtaining, by the encoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the chroma residual signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 19. The method for video encoding of claim 18, further comprising: obtaining, by the encoder, clipped results of one or more spatial neighboring samples from the chroma residual signal; and deriving, by the encoder, a chroma ALF input based on the clipped results. 20. The method for video encoding of claim 14, further comprising: obtaining, by the encoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-chroma SAO signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 21. The method for video encoding of claim 20, further comprising: Attorney Ref.: 186015.20176 obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples from the pre-chroma SAO signal and the current chroma sample; and deriving, by the encoder, a chroma ALF input based on the clipped results. 22. The method for video encoding of claim 20, further comprising: obtaining, by the encoder, clipped results based on differences between surrounding samples from the pre-chroma SAO signal and collocated samples from the pre-chroma SAO signal, and clipped results based on differences between collocated samples in pre-chroma SAO signal and current chroma sample; and deriving, by the encoder, a chroma ALF input based on the clipped results. 23. The method for video encoding of claim 14, further comprising: obtaining, by the encoder, an adaptive loop filter (ALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre-chroma deblocking signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 24. The method for video encoding of claim 23, further comprising: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples in the pre-chroma deblocking signal and the current chroma sample; and deriving, by the encoder, a chroma ALF input based on the clipped results. 25. The method for video encoding of claim 23, further comprising: Attorney Ref.: 186015.20176 obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples in the pre-chroma deblocking signal and collocated samples in pre- chroma deblocking signal, and clipped results based on differences between collocated samples in pre-chroma deblocking signal and current chroma sample; and deriving, by the encoder, a chroma ALF input based on the clipped results. 26. The method for video encoding of claim 14, wherein one or more surrounding samples are from a combination of following signals: (i) the chroma prediction signal, (ii) the chroma residual signal, (iii) the pre-chroma SAO signal, or (iv) the pre-chroma deblocking signal. 27. A method for video decoding, comprising: obtaining, by a decoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of following signals: (i) a luma prediction signal, (ii) a luma residual signal, (iii) a pre-luma sample adaptive offset (SAO) signal, or (iv) a pre-luma deblocking signal; and obtaining, by the decoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample. 28. The method for video decoding of claim 27, further comprising: obtaining, by the decoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the luma prediction signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 29. The method for video decoding of claim 28, further comprising: Attorney Ref.: 186015.20176 obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the luma prediction signal and the current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. 30. The method for video decoding of claim 28, further comprising: obtaining, by the decoder, clipped results based on differences between surrounding samples in the luma prediction signal and collocated samples in the luma prediction signal, and clipped results based on differences between collocated samples in the luma prediction signal and current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. 31. The method for video decoding of claim 27, comprising: obtaining, by the decoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the luma residual signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 32. The method for video decoding of claim 31, further comprising: obtaining, by the decoder, clipped results of one or more spatial neighboring samples in the luma residual signal; and deriving, by the decoder, the CCALF input based on the clipped results. 33. The method for video decoding of claim 27, comprising: obtaining, by the decoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre- Attorney Ref.: 186015.20176 luma SAO signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 34. The method for video decoding of claim 33, further comprising: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples in the pre-luma SAO signal and the current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. 35. The method for video decoding of claim 33, further comprising: obtaining, by the decoder, clipped results based on differences between surrounding samples from the pre-luma SAO signal and collocated samples from the pre-luma SAO signal, and clipped results based on differences between collocated samples in the pre-luma SAO signal and current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. 36. The method for video decoding of claim 27, comprising: obtaining, by the decoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre- luma deblocking signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 37. The method for video decoding of claim 36, further comprising: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the pre-luma deblocking signal and the current corresponding luma sample; and Attorney Ref.: 186015.20176 deriving, by the decoder, the CCALF input based on the clipped results. 38. The method for video decoding of claim 36, further comprising: obtaining, by the decoder, clipped results based on differences between one or more spatial neighboring samples from the pre-luma deblocking signal and collocated samples from the pre-luma deblocking signal, and clipped results based on differences between collocated samples in the pre-luma deblocking signal and current corresponding luma sample; and deriving, by the decoder, the CCALF input based on the clipped results. 39. The method for video decoding of claim 27, wherein one or more spatial neighboring samples are from a combination of following signals: (i) the luma prediction signal; (ii) the luma residual signal; (iii) the pre-luma SAO signal; or (iv) the pre-luma deblocking signal. 40. A method for video encoding, comprising: obtaining, by an encoder, one or more spatial neighboring samples associated with a current chroma sample, wherein the one or more spatial neighboring samples are from at least one of following signals: (i) a luma prediction signal, (ii) a luma residual signal, (iii) a pre-luma sample adaptive offset (SAO) signal, or (iv) a pre-luma deblocking signal; and obtaining, by the encoder, a filtered chroma sample, based on the one or more spatial neighboring samples associated with the current chroma sample. 41. The method for video encoding of claim 40, further comprising: obtaining, by the encoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the luma prediction signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. Attorney Ref.: 186015.20176 42. The method for video encoding of claim 41, further comprising: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples from the luma prediction signal and the current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. 43. The method for video encoding of claim 41, further comprising: obtaining, by the encoder, clipped results based on differences between surrounding samples the luma prediction signal and collocated samples in the luma prediction signal, and clipped results based on differences between collocated samples in the luma prediction signal and current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. 44. The method for video encoding of claim 40, further comprising: obtaining, by the encoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the luma residual signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 45. The method for video encoding of claim 44, further comprising: obtaining, by the encoder, clipped results of one or more spatial neighboring samples from the luma residual signal; and deriving, by the encoder, the CCALF input based on the clipped results. 46. The method for video encoding of claim 40, comprising: Attorney Ref.: 186015.20176 obtaining, by the encoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre- luma SAO signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 47. The method for video encoding of claim 46, further comprising: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples from the pre-luma SAO signal and the current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. 48. The method for video encoding of claim 46, further comprising: obtaining, by the encoder, clipped results based on differences between surrounding samples from the pre-luma SAO signal and collocated samples from the pre-luma SAO signal, and clipped results based on differences between collocated samples in the pre-luma SAO signal and current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. 49. The method for video encoding of claim 40, further comprising: obtaining, by the encoder, a cross-component adaptive loop filter (CCALF) filtered chroma sample based on the one or more spatial neighboring samples associated with the pre- luma deblocking signal and one or more filter coefficients, wherein the one or more filter coefficients are associated with different filter shapes. 50. The method for video encoding of claim 49, further comprising: Attorney Ref.: 186015.20176 obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples from the pre-luma deblocking signal and the current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. 51. The method for video encoding of claim 49, further comprising: obtaining, by the encoder, clipped results based on differences between one or more spatial neighboring samples from the pre-luma deblocking signal and collocated samples from the pre-luma deblocking signal, and clipped results based on differences between collocated samples in the pre-luma deblocking signal and current corresponding luma sample; and deriving, by the encoder, the CCALF input based on the clipped results. 52. The method for video encoding of claim 40, wherein one or more spatial neighboring samples are from a combination of following signals: (i) the luma prediction signal; (ii) the luma residual signal; (iii) the pre-luma SAO signal; or (iv)the pre-luma deblocking signal. 53. A method for video decoding, comprising: obtaining, by a decoder, coding information associated with a coding block, wherein the coding information includes a first flag indicating that the coding block is coded with a skip mode and a second flag indicating that the coding block is coded with at least one of the following modes: an intra mode, an inter P mode, or an inter B mode, to derive new classifiers for an online adaptive loop filter (ALF) process; and generating, by the decoder, a new classifier for the online adaptive ALF process based on the coding information. Attorney Ref.: 186015.20176 54. The method for video decoding of claim 53, further comprising: using the first flag to derive the new classifier for the online ALF process 55. The method for video decoding of claim 54, wherein the new classifier includes two classes corresponding to whether the coding block is coded with the skip mode. 56. The method for video decoding of claim 54, wherein the new classifier combines skip mode information with at least one of: edge offset(EO) (edge-based classifier) information, or band offset (BO) (band-based classifier) information. 57. The method for video decoding of claim 53, further comprising: recording, at the decoder, that the coding block is coded with at least one of following modes: (i) intra mode, (ii) inter P mode, or (iii) inter B mode; and generating, at the decoder, the new classifier for the online ALF process based on the recording. 58. The method for video decoding of claim 57, wherein the new classifier includes three classes corresponding to the coding block is coded with intra mode, inter P mode, or inter B mode. 59. The method for video decoding of claim 57, wherein the new classifier combines: information that the coding block is coded with at least one of: intra mode, inter P mode, or inter B mode, with at least one of: edge offset (EO) (edge based classifier) information, or band offset(BO) (band based classifier) information. 60. The method for video decoding of claim 53, further comprising: Attorney Ref.: 186015.20176 determining, at the decoder, that whether the coding block is coded with skip mode; determining, at the decoder, that the coding block is coded with one of the following modes: (i) intra mode; (ii) inter P mode; or (iii) inter B mode; and generating, at the decoder, the new classifier based on the determined modes. 61. A method for video encoding, comprising: obtaining, by an encoder, coding information associated with a coding block, wherein the coding information includes information whether the coding block is coded with a skip mode and information that the coding block is coded with at least one of the following: an intra mode, an inter P mode, or an inter B mode, to derive new classifiers for an online adaptive loop filter (ALF) process; and generating, by the encoder, a new classifier for the online ALF process based on the coding information. 62. The method for video encoding of claim 61, wherein whether the coding block is coded with the skip mode during an encoding process is utilized to derive the new classifier for the online ALF process. 63. The method for video encoding of claim 62, wherein the new classifier includes two classes corresponding to whether the coding block is coded with the skip mode. 64. The method for video encoding of claim 62, wherein the new classifier combines skip mode information with edge offset (EO) (edge based classifier) information or band offset (BO) (band based classifier) information. 65. The method for video encoding of claim 61, further comprising: Attorney Ref.: 186015.20176 recording, at the encoder, that the coding block is coded with at least one of: (i) intra mode, (ii) inter P mode, or (iii) inter B mode; and generating, by the encoder, the new classifier for the online ALF process based on the recording. 66. The method for video encoding of claim 65, wherein the new classifier includes three classes corresponding to the coding block is coded with intra mode, inter P mode, or inter B mode. 67. The method for video encoding of claim 65, wherein the new classifier combines: information that the coding block is coded with at least one of: intra mode, inter P mode, or inter B mode, with at least one of: edge offset (EO) (edge based classifier) information, or (BO) (band based classifier) information. 68. The method for video encoding of claim 65, further comprising: determining, at the encoder, whether the coding block is coded with skip mode; determining, at the encoder, that the coding block is coded with one of the following modes: (i) intra mode; (ii) inter P mode; or (iv) inter B mode; and generating the new classifier based on the modes. 69. An apparatus for video decoding, comprising: one or more processors; and a memory coupled to the one or more processors and configured to store instructions executable by the one or more processors, wherein the one or more processors, upon execution of the instructions are configured to perform a method in any one of claims: 1-13, 27-39, and 53- 60. Attorney Ref.: 186015.20176 70. An apparatus for video encoding, comprising: one or more processors; and a memory coupled to the one or more processors and configured to store instructions executable by the one or more processors, wherein the one or more processors, upon execution of the instructions are configured to perform a method in any one of claims: 14-26, 40-52, and 61-68. 71. A non-transitory computer readable storage medium for storing computer-executable instructions that, when executed by one or more computer processors, cause the one or more computer processors to receive a bitstream and perform a method in any one of claims: 1-13, 27- 39, and 53-60. 72. A non-transitory computer readable storage medium for storing computer-executable instructions that, when executed by one or more computer processors, cause the one or more computer processors to perform a method in any one of claims: 14-26, 40-52, and 61-68 to generate and transmit a bitstream. 73. A bitstream to be decoded by a decoding method in any one of claims: 1-13, 27, 39, and 53-60. 74. A bitstream generated by an encoding method in any one of claims 14-26, 40-52, and 61- 68.